| Compensation and Retirement Disclosure [Abstract] | Period [Axis] |
|---|
2016-01-01 - 2016-12-31 |
|---|
Compensation and Retirement Disclosure [Abstract] | |
Combined Activity in Corporations Defined Benefit Pension Plans | We use a December 31 measurement date for our defined benefit plans. Combined activity in our defined benefit pension plans was as follows: | | | | | | | | | | | | | | 2016 | | 2015 | | 2014 | Change in benefit obligation: | | | | | | Benefit obligation at beginning of year | $ | 194,140 |
| | $ | 199,637 |
| | $ | 163,876 |
| Interest cost | 6,958 |
| | 8,210 |
| | 8,002 |
| Actuarial (gain) loss | (8,298 | ) | | (6,489 | ) | | 34,438 |
| Benefits paid | (16,049 | ) | | (7,218 | ) | | (6,679 | ) | Benefit obligation at end of year | 176,751 |
| | 194,140 |
| | 199,637 |
| Change in plan assets: | | | | | | Fair value of plan assets at beginning of year | 163,270 |
| | 168,185 |
| | 164,769 |
| Actual return on plan assets | 5,174 |
| | 1,567 |
| | 9,428 |
| Employer contributions | 4,819 |
| | 736 |
| | 667 |
| Benefits paid | (16,049 | ) | | (7,218 | ) | | (6,679 | ) | Fair value of plan assets at end of year | 157,214 |
| | 163,270 |
| | 168,185 |
| Funded status of the plan at end of year and accrued (benefit) liability recognized | $ | 19,537 |
| | $ | 30,870 |
| | $ | 31,452 |
| Accumulated benefit obligation at end of year | $ | 176,751 |
| | $ | 194,140 |
| | $ | 199,637 |
|
|
Disaggregated Information Related to Corporations Defined Benefit Pension Plans | Certain disaggregated information related to our defined benefit pension plans as of year-end was as follows: | | | | | | | | | | | | | | | | | | Retirement Plan | | Restoration Plan | | 2016 | | 2015 | | 2016 | | 2015 | Projected benefit obligation | $ | 160,778 |
| | $ | 174,429 |
| | $ | 15,973 |
| | $ | 19,711 |
| Accumulated benefit obligation | 160,778 |
| | 174,429 |
| | 15,973 |
| | 19,711 |
| Fair value of plan assets | 157,214 |
| | 163,270 |
| | — |
| | — |
| Funded status of the plan at end of year and accrued (benefit) liability recognized | 3,564 |
| | 11,159 |
| | 15,973 |
| | 19,711 |
|
|
Net Periodic Benefit Cost (Benefit) | The components of the combined net periodic cost (benefit) for our defined benefit pension plans are presented in the table below. Supplemental executive retirement plan (“SERP”) settlement costs were related to the retirement of a former executive officer. | | | | | | | | | | | | | | 2016 | | 2015 | | 2014 | Expected return on plan assets, net of expenses | $ | (11,558 | ) | | $ | (11,932 | ) | | $ | (12,514 | ) | Interest cost on projected benefit obligation | 6,958 |
| | 8,210 |
| | 8,002 |
| Net amortization and deferral | 6,247 |
| | 6,995 |
| | 2,687 |
| SERP settlement costs | 1,027 |
| | — |
| | — |
| Net periodic expense (benefit) | $ | 2,674 |
| | $ | 3,273 |
| | $ | (1,825 | ) |
|
Defined Benefit Pension Plans Recognized as Component of Other Comprehensive Income | Amounts related to our defined benefit pension plans recognized as a component of other comprehensive income were as follows: | | | | | | | | | | | | | | 2016 | | 2015 | | 2014 | Net actuarial gain (loss) | $ | 9,188 |
| | $ | 3,118 |
| | $ | (34,837 | ) | Deferred tax (expense) benefit | (3,216 | ) | | (1,091 | ) | | 12,193 |
| Other comprehensive income (loss), net of tax | $ | 5,972 |
| | $ | 2,027 |
| | $ | (22,644 | ) |
|
Defined Benefit Pension Plans Not Recognized as Component of Combined Net Period Benefit Cost | We expect to recognize approximately $5.4 million of the net actuarial loss reported in the following table as of December 31, 2016 as a component of net periodic benefit cost during 2017. | | | | | | | | | | 2016 | | 2015 | Net actuarial loss | $ | (62,732 | ) | | $ | (71,920 | ) | Deferred tax benefit | 21,956 |
| | 25,172 |
| Amounts included in accumulated other comprehensive loss, net of tax | $ | (40,776 | ) | | $ | (46,748 | ) |
|
Weighted-Average Assumptions Used to Determine Benefit Obligations | The weighted-average assumptions used to determine the benefit obligations as of the end of the years indicated and the net periodic benefit cost for the years indicated are presented in the table below. Because the plans were frozen, increases in compensation are not considered after 2001. | | | | | | | | | | | 2016 | | 2015 | | 2014 | Benefit obligations: | | | | | | Discount rate | 4.24 | % | | 4.55 | % | | 4.20 | % | Net periodic benefit cost: | | | | | | Discount rate | 4.55 | % | | 4.20 | % | | 5.00 | % | Expected return on plan assets | 7.25 |
| | 7.25 |
| | 7.25 |
|
|
Fair Value of Plan Assets | The major categories of assets in our Retirement Plan as of year-end are presented in the following table. Assets are segregated by the level of the valuation inputs within the fair value hierarchy established by ASC Topic 820 “Fair Value Measurements and Disclosures,” utilized to measure fair value (see Note 18 - Fair Value Measurements). Our Restoration Plan is unfunded. | | | | | | | | | | 2016 | | 2015 | Level 1: | | | | Mutual funds | $ | 153,765 |
| | $ | 162,379 |
| Cash and cash equivalents | 3,208 |
| | 322 |
| Level 2: | | | | U.S. government agency securities | 241 |
| | 316 |
| States and political subdivisions | — |
| | 253 |
| Total fair value of plan assets | $ | 157,214 |
| | $ | 163,270 |
|
|
Expected Future Benefit Payments Related to Defined Benefit Plans | As of December 31, 2016, expected future benefit payments related to our defined benefit plans were as follows: | | | | | 2017 | $ | 8,947 |
| 2018 | 9,417 |
| 2019 | 9,864 |
| 2020 | 10,268 |
| 2021 | 10,581 |
| 2022 through 2026 | 56,102 |
| | $ | 105,179 |
|
|
Summary of Activity in Corporation's Active Stock Plans | A combined summary of activity in our active stock plans is presented in the table. Performance stock units outstanding are presented assuming attainment of the maximum payout rate as set forth by the performance criteria. The target award level for performance stock units granted in 2016 was 28,420. As of December 31, 2016, there were 1,452,452 shares remaining available for grant for future awards. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Director Deferred Stock Units Outstanding | | Non-Vested Stock Awards/Stock Units Outstanding | | Performance Stock Units Outstanding | | Stock Options Outstanding | | | Number of Units | | Weighted- Average Fair Value at Grant | | Number of Shares/Units | | Weighted- Average Fair Value at Grant | | Number of Units | | Weighted- Average Fair Value at Grant | | Number of Shares | | Weighted- Average Exercise Price | January 1, 2014 | | 33,224 |
| | $ | 56.22 |
| | 199,740 |
| | $ | 55.32 |
| | — |
| | $ | — |
| | 4,738,690 |
| | $ | 54.35 |
| Authorized | | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| Granted | | 5,643 |
| | 78.04 |
| | 32,050 |
| | 78.92 |
| | — |
| | — |
| | 917,750 |
| | 78.93 |
| Exercised/vested | | — |
| | — |
| | (56,300 | ) | | 52.46 |
| | — |
| | — |
| | (560,291 | ) | | 52.04 |
| Forfeited/expired | | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | (66,267 | ) | | 62.21 |
| December 31, 2014 | | 38,867 |
| | 59.39 |
| | 175,490 |
| | 60.55 |
| | — |
| | — |
| | 5,029,882 |
| | 58.99 |
| Authorized | | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| Granted | | 6,576 |
| | 72.94 |
| | 53,990 |
| | 65.11 |
| | — |
| | — |
| | 890,940 |
| | 65.11 |
| Exercised/vested | | — |
| | — |
| | (56,300 | ) | | 48.00 |
| | — |
| | — |
| | (287,326 | ) | | 51.70 |
| Forfeited/expired | | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | (21,256 | ) | | 66.72 |
| December 31, 2015 | | 45,443 |
| | 61.35 |
| | 173,180 |
| | 66.05 |
| | — |
| | — |
| | 5,612,240 |
| | 60.30 |
| Authorized | | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| Granted | | 8,216 |
| | 63.25 |
| | 132,800 |
| | 76.07 |
| | 42,630 |
| | 69.70 |
| | — |
| | — |
| Exercised/vested | | — |
| | — |
| | (49,130 | ) | | 54.56 |
| | — |
| | — |
| | (1,476,841 | ) | | 53.40 |
| Forfeited/expired | | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| | (46,371 | ) | | 71.04 |
| December 31, 2016 | | 53,659 |
| | $ | 61.48 |
| | 256,850 |
| | $ | 73.43 |
| | 42,630 |
| | $ | 69.70 |
| | 4,089,028 |
| | $ | 62.67 |
|
|
Options Outstanding and Exercisable | Other information regarding options outstanding and exercisable as of December 31, 2016 is as follows: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Options Outstanding | | Options Exercisable | Range of Exercise Prices | | Number of Shares | | Weighted- Average Exercise Price | | Weighted- Average Remaining Contractual Life in Years | | Number of Shares | | Weighted- Average Exercise Price | $ | 45.01 |
| | to | | $ | 50.00 |
| | 469,015 |
| | $ | 48.19 |
| | 3.93 | | 469,015 |
| | $ | 48.19 |
| 50.01 |
| | to | | 55.00 |
| | 1,385,938 |
| | 52.76 |
| | 3.89 | | 1,385,938 |
| | 52.76 |
| 65.01 |
| | to | | 70.00 |
| | 860,190 |
| | 65.11 |
| | 8.36 | | 200,611 |
| | 65.11 |
| 70.01 |
| | to | | 75.00 |
| | 518,010 |
| | 71.38 |
| | 6.53 | | 379,849 |
| | 71.38 |
| 75.01 |
| | to | | 80.00 |
| | 855,875 |
| | 78.94 |
| | 7.42 | | 420,250 |
| | 78.94 |
| | | | | Total | | 4,089,028 |
| | 62.67 |
| | 5.91 | | 2,855,663 |
| | 59.21 |
|
|
Shares Issued in Connection With Stock Compensation Awards | Shares issued in connection with stock compensation awards are issued from available treasury shares. If no treasury shares are available, new shares are issued from available authorized shares. Shares issued in connection with stock compensation awards along with other related information were as follows: | | | | | | | | | | | | | | 2016 | | 2015 | | 2014 | New shares issued from available authorized shares | — |
| | — |
| | — |
| Issued from available treasury stock | 1,509,121 |
| | 337,056 |
| | 601,851 |
| Total | 1,509,121 |
| | 337,056 |
| | 601,851 |
| Proceeds from stock option exercises | $ | 78,866 |
| | $ | 14,853 |
| | $ | 29,158 |
| Intrinsic value of stock options exercised | 30,935 |
| | 5,766 |
| | 13,714 |
| Fair value of stock awards/units vested | 3,679 |
| | 3,728 |
| | 4,346 |
|
|
Stock-Based Compensation Expense | Stock-based compensation expense and the related income tax benefit is presented in the following table. The service period for performance stock units granted in 2016 begins on January 1, 2017. | | | | | | | | | | | | | | 2016 | | 2015 | | 2014 | Stock options | $ | 8,235 |
| | $ | 9,660 |
| | $ | 9,142 |
| Non-vested stock awards/stock units | 3,044 |
| | 2,597 |
| | 2,920 |
| Deferred stock-units | 520 |
| | 480 |
| | 441 |
| Performance stock units | — |
| | — |
| | — |
| Total | $ | 11,799 |
| | $ | 12,737 |
| | $ | 12,503 |
| Income tax benefit | $ | 4,130 |
| | $ | 4,458 |
| | $ | 4,376 |
|
|
Unrecognized Stock-Based Compensation Expense | Unrecognized stock-based compensation expense and the weighted-average period over which the expense is expected to be recognized at December 31, 2016 is presented in the table below. Unrecognized stock-based compensation expense related to performance stock units is presented assuming attainment of the maximum payout rate as set forth by the performance criteria. | | | | | | | | Unrecognized Expense | | Weighted-Average Number of Years for Expense Recognition | Stock options | $ | 12,446 |
| | 2.1 | Non-vested stock awards/stock units | 10,413 |
| | 3.2 | Performance stock units | 2,971 |
| | 3.0 | Total | $ | 25,830 |
| | |
|
Assumptions Used to Determine The Fair Value of Options Granted | The assumptions used to determine the fair value of options granted are detailed in the table below. | | | | | | | | 2015 | | 2014 | Weighted-average risk-free interest rate | 2.05 | % | | 2.33 | % | Dividend yield | 3.02 |
| | 2.71 |
| Weighted-average expected market price volatility | 26.48 |
| | 26.66 |
| Weighted-average expected term | 5.7 years |
| | 7.1 years |
|
|