| Compensation and Retirement Disclosure [Abstract] | Period [Axis] |
|---|
2016-01-01 - 2016-12-31 |
|---|
Compensation and Retirement Disclosure [Abstract] | |
Schedule of changes in projected benefit obligations [Table Text Block] | The change in benefit obligations and the fair value of plans assets follows: | | | | | | | | | | December 31, | | 2016 | | 2015 | Change in benefit obligation | | | | Projected benefit obligation at beginning of year | $ | 27,228 |
| | $ | 35,876 |
| Service cost | 370 |
| | 35 |
| Interest cost | 1,243 |
| | 1,486 |
| Actuarial (gains)/losses | 1,150 |
| | (2,445 | ) | New longevity assumptions | (447 | ) | | (340 | ) | Amendments | 341 |
| | — |
| Curtailments | — |
| | (404 | ) | Settlements | (4,873 | ) | | (6,186 | ) | Benefits paid | (179 | ) | | (794 | ) | Projected benefit obligation at end of year | $ | 24,833 |
| | $ | 27,228 |
| Accumulated benefit obligation at end of year | $ | 24,833 |
| | $ | 27,228 |
|
|
Schedule of changes in fair value of plan sssets [Table Text Block] | | | | | | | | | | | December 31, | | 2016 | | 2015 | Change in fair value of plan assets | | | | Fair value of plan assets at beginning of year | $ | 15,216 |
| | $ | 21,567 |
| Actual return on plan assets | 400 |
| | (135 | ) | Plan expenses, including PBGC premiums | (727 | ) | | (536 | ) | Employer contributions | 1,672 |
| | 1,300 |
| Settlements | (4,873 | ) | | (6,186 | ) | Benefits paid | (179 | ) | | (794 | ) | Fair value of plan assets at end of year | $ | 11,509 |
| | $ | 15,216 |
|
|
Schedule of net funded status [Table Text Block] | | | | | | | | | | | December 31, | | 2016 | | 2015 | Funded status of the plans | | | | Fair value of plan assets | $ | 11,509 |
| | $ | 15,216 |
| Projected benefit obligation | 24,833 |
| | 27,228 |
| Funded status of the plans | $ | (13,324 | ) | | $ | (12,012 | ) |
|
Schedule of amounts recognized in balance sheet [Table Text Block] | | | | | | | | | | | December 31, | | 2016 | | 2015 | Amounts reported in the consolidated balance sheets | | | | Current liability | $ | (83 | ) | | $ | (499 | ) | Noncurrent liability | (13,241 | ) | | (11,513 | ) | Funded status of the plans | $ | (13,324 | ) | | $ | (12,012 | ) |
|
Schedule of amounts in accumulated other comprehensive income [Table Text Block] | Amounts included in accumulated other comprehensive income (loss), related to our defined benefit pension plans follow: | | | | | | | | | | | | | | | | | | At December 31, 2016 | | At December 31, 2015 | | Pretax | | Net of Tax | | Pretax | | Net of Tax | Amounts reported in accumulated other comprehensive income | | | | | | | Unrecognized net actuarial loss | $ | 10,675 |
| | $ | 6,456 |
| | $ | 11,836 |
| | $ | 7,150 |
| Unrecognized prior service cost | 341 |
| | 206 |
| | — |
| | — |
| | $ | 11,016 |
| | $ | 6,662 |
| | $ | 11,836 |
| | $ | 7,150 |
|
|
Schedule of amounts in accumulated other comprehensive income (loss) to be recognized over next fiscal year [Table Text Block] | The total amortization associated with these amounts that is expected to be recognized in net periodic benefit expense for 2017 follows:
| | | | | | | | | | Year ending December 31, 2017 | | Pretax | | Net of Tax | Amortization of Costs Expected to be Recognized Next Year | | | | Unrecognized net actuarial loss | $ | 949 |
| | $ | 569 |
| Unrecognized prior service cost | 64 |
| | 38 |
| | $ | 1,013 |
| | $ | 607 |
|
|
Schedule of accumulated benefit obligations in excess of fair value of plan assets [Table Text Block] | The aggregate projected benefit obligation, accumulated benefit obligation and fair value of plan assets for plans in which the fair value of plan assets is less than either the projected benefit obligation or accumulated benefit obligation follow:
| | | | | | | | | | December 31, | | 2016 | | 2015 | For pension plans with accumulated benefit obligations in excess of plan assets | | | | Projected benefit obligation | $ | 24,833 |
| | $ | 27,228 |
| Accumulated benefit obligation | 24,833 |
| | 27,228 |
| Fair value of plan assets | 11,509 |
| | 15,216 |
|
|
Schedule of assumptions used [Table Text Block] | The actuarial assumptions follow. The discount rates were used to measure the year-end benefit obligation and compute pension expense for the subsequent year.
| | | | | | | | | | | December 31, | | 2016 | | 2015 | | 2014 | Actuarial assumptions | | | | | | Discount rate | 4.20 | % | | 4.70 | % | | 4.30 | % | Expected long-term rate of return on plan assets | 5.00 |
| | 7.25 |
| | 7.50 |
|
|
Components of pension expense (income) [Table Text Block] | Net periodic benefit expense (income) associated with the defined benefit pension plans included the following components:
| | | | | | | | | | | | | | Year Ended December 31, | | 2016 | | 2015 | | 2014 | Components of pension expense (income) | | | | | | Service costs--increase in benefit obligation earned | $ | 370 |
| | $ | 35 |
| | $ | 51 |
| Interest cost on projected benefit obligation | 1,243 |
| | 1,486 |
| | 1,618 |
| Expected return on plan assets | (1,044 | ) | | (1,576 | ) | | (1,993 | ) | Curtailment loss | — |
| | 49 |
| | — |
| Settlement loss | 2,346 |
| | 2,915 |
| | 2,065 |
| Amortization of net actuarial loss | 951 |
| | 1,400 |
| | 708 |
| Amortization of prior service cost | — |
| | 6 |
| | 14 |
| Net pension expense of defined benefit pension plans | $ | 3,866 |
| | $ | 4,315 |
| | $ | 2,463 |
|
|
Schedule of allocation of plan assets [Table Text Block] | The fair values of our pension plan assets at December 31, 2016 by asset category, using the three-level hierarchy of fair value inputs, were as follows:
| | | | | | | | | | | | | | | | | | | | | | Fair Value Measurements at December 31, 2016 Using: | Description | | Total Carrying Value at December 31, 2016 | | Quoted prices in active markets (Level 1) | | Significant other observable inputs (Level 2) | | Significant unobservable inputs (Level 3) | Asset Category | | | | | | | | | Money market funds | | $ | 2,882 |
| | $ | — |
| | $ | 2,882 |
| | $ | — |
| U.S. large-cap equities | | |
| | |
| | |
| | |
| Growth | | 687 |
| | 687 |
| | — |
| | — |
| Value | | 729 |
| | 729 |
| | — |
| | — |
| U.S. small/mid-cap equities | | |
| | |
| | |
| | |
| Growth | | 339 |
| | 339 |
| | — |
| | — |
| Value | | 339 |
| | 339 |
| | — |
| | — |
| International equities | | |
| | |
| | |
| | |
| Growth | | 443 |
| | 443 |
| | — |
| | — |
| Value | | 514 |
| | 514 |
| | — |
| | — |
| Fixed income | | 4,669 |
| | 4,669 |
| | — |
| | — |
| Multiclass world-allocation mutual funds | | 907 |
| | 907 |
| | — |
| | — |
| | | $ | 11,509 |
| | $ | 8,627 |
| | $ | 2,882 |
| | $ | — |
|
The fair values of our pension plan assets at December 31, 2015 by asset category, using the three-level hierarchy of fair value inputs, were as follows:
| | | | | | | | | | | | | | | | | | | | | | Fair Value Measurements at December 31, 2015 Using: | Description | | Total Carrying Value at December 31, 2015 | | Quoted prices in active markets (Level 1) | | Significant other observable inputs (Level 2) | | Significant unobservable inputs (Level 3) | Asset Category | | | | | | | | | Money market funds | | $ | 2,794 |
| | $ | — |
| | $ | 2,794 |
| | $ | — |
| U.S. large-cap equities | | |
| | |
| | |
| | |
| Growth | | 1,869 |
| | 1,869 |
| | — |
| | — |
| Value | | 1,492 |
| | 1,492 |
| | — |
| | — |
| U.S. small/mid-cap equities | | |
| | |
| | |
| | |
| Growth | | 781 |
| | 781 |
| | — |
| | — |
| Value | | 1,003 |
| | 1,003 |
| | — |
| | — |
| International equities | | |
| | |
| | |
| | |
| Growth | | 1,270 |
| | 1,270 |
| | — |
| | — |
| Value | | 1,183 |
| | 1,183 |
| | — |
| | — |
| Fixed income | | 3,035 |
| | 3,035 |
| | — |
| | — |
| Multiclass world-allocation mutual funds | | 1,789 |
| | 1,789 |
| | — |
| | — |
| | | $ | 15,216 |
| | $ | 12,422 |
| | $ | 2,794 |
| | $ | — |
|
|
Schedule of expected benefit payments [Table Text Block] | The benefits, as of December 31, 2016, expected to be paid to defined-benefit plan participants in each of the next five years, and in the aggregate for the five years thereafter, follow:
| | | | | | | | Participants Benefits | Estimated future payments | | | Year ending December 31, 2017 | | $ | 659 |
| 2018 | | 878 |
| 2019 | | 981 |
| 2020 | | 1,088 |
| 2021 | | 1,167 |
| Years 2022 to 2026 | | 6,677 |
|
|
Schedule of multiemployer plans [Table Text Block] | Our participation in the multiemployer defined benefit pension plans is summarized in the table below. The “EIN/Pension Plan Number” column provides the Employer Identification Number (“EIN”) and the three-digit plan number. The most recent Pension Protection Act of 2006 (the “PPA”) zone status is from the Form 5500, “Annual Return/Report of Employee Benefit Plan,” filed by the plan and certified by the plan's actuary. The PPA zone status describes plans that are underfunded. Among other factors, plans in the “critical” red zone are generally less than 65% funded; plans in the “endangered” yellow zone are less than 80% funded; and, plans in the “safe” green zone are at least 80% funded.
| | P. | Defined Benefit Pension Plans (continued) |
| | | | | | | | | | | | | | | | | | | | | | | | | | Pension Fund | | EIN/Pension Plan Number | | Pension Protection Act Zone Status | | FIP/RP Status Pending Implemented | | Davey Tree Contributions | | Surcharge Imposed | | Expiration Dates of Bargaining Agreement | | | 2016 | | 2015 | | | 2016 | | 2015 | | 2014 | | | National Electric Benefit Fund | | 53-0181657/001 | | Green | | Green | | No | | $ | 712 |
| | $ | 774 |
| | $ | 743 |
| | No | | Ranging from June 30, 2017 to December 31, 2018 | Eighth District Electrical Pension Fund | | 84-6100393/001 | | Green | | Green | | No | | 90 |
| | 119 |
| | 105 |
| | No | | December 31, 2017 | | | | | | | | | | | $ | 802 |
| | $ | 893 |
| | $ | 848 |
| | | | |
|