Entity information:
Federal and State Income Taxes

The Tax Cuts and Jobs Act (the "Act"), which was enacted on December 22, 2017, reduces the federal corporate tax rate from 35% to 21% for periods beginning January 1, 2018. Provisions of the Act are broad and complex. As result, we are still evaluating the impact that certain aspects of the Act will have on the Company's financial position and results of operations, including recognition and measurement of deferred tax assets and liabilities and the determination of effective current and deferred federal and state income tax rates. We have made reasonable estimates of the Act's impact on net deferred tax assets and recorded a provisional adjustment of $9.5 million, including $6.4 million of net deferred tax assets resulting from temporary differences recognized in Accumulated other comprehensive income on the Company's balance sheets. Additionally, we recognized a provisional adjustment of $2.2 million for deferred taxes resulting from executive compensation that may no longer be deductible.

We are not aware of any material areas where we were not able to determine provisional amounts. However, accounting for income tax effects of the Act is still in process and provisional adjustments recognized in 2017 may be adjusted as a result of our on-going evaluation, including subsequent guidance provided by federal and state taxing authorities and other information as it becomes available.

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. As a result of the Act, deferred tax balances at December 31, 2017 generally have been revalued from the previous combined federal and state statutory rate of 38.9% to 25.5%. Significant components of deferred tax assets and liabilities are as follows (in thousands):

 
December 31,
 
2017
 
2016
Deferred tax assets:
 
 
 
Available for sale securities mark to market
$
12,083

 
$
5,779

Share-based compensation
7,598

 
9,360

Credit loss allowances
58,666

 
99,191

Valuation adjustments
8,102

 
12,222

Deferred compensation
12,215

 
30,262

Unearned fees
9,265

 
11,877

Other
30,859

 
42,541

Total deferred tax assets
138,788

 
211,232

 
 
 
 
Deferred tax liabilities:
 
 
 
Depreciation
15,817

 
25,877

Mortgage servicing rights
63,112

 
92,748

Lease financing
9,973

 
17,923

Other
34,880

 
45,363

Total deferred tax liabilities
123,782

 
181,911

Net deferred tax assets
$
15,006

 
$
29,321



No valuation allowance was necessary on deferred tax assets as of December 31, 2017 and 2016.

The significant components of the provision for income taxes attributable to continuing operations for BOK Financial are shown below (in thousands):
 
Year Ended December 31,
 
2017
 
2016
 
2015
Current income tax expense:
 
 
 
 
 
Federal
$
141,607

 
$
107,379

 
$
117,566

State
14,592

 
11,028

 
12,397

Total current income tax expense
156,199

 
118,407

 
129,963

 
 
 
 
 
 
Deferred income tax expense:
 
 
 
 
 
Federal
25,525

 
(11,340
)
 
8,397

State
869

 
(690
)
 
1,024

Total deferred income tax expense
26,394

 
(12,030
)
 
9,421

Total income tax expense
$
182,593

 
$
106,377

 
$
139,384




The reconciliations of income attributable to continuing operations at the U.S. federal statutory tax rate to income tax expense are as follows (in thousands):
 
Year Ended December 31,
 
2017
 
2016
 
2015
Amount:
 
 
 
 
 
Federal statutory tax
$
181,397

 
$
118,530

 
$
151,075

Tax exempt revenue
(12,402
)
 
(10,544
)
 
(9,553
)
Effect of state income taxes, net of federal benefit
10,701

 
6,478

 
9,082

Utilization of tax credits:
 
 
 
 
 
Low-income housing tax credits, net of amortization
(5,356
)
 
(4,171
)
 
(3,874
)
Other tax credits
(1,455
)
 
(2,085
)
 
(2,085
)
Bank-owned life insurance
(3,121
)
 
(2,911
)
 
(3,264
)
Share-based compensation
(2,817
)
 

 

Revaluation of net deferred tax assets due to change in federal tax rates
9,456

 

 

Write-off of deferred tax assets related to executive compensation
2,216

 

 

Other, net
3,974

 
1,080

 
(1,997
)
Total income tax expense
$
182,593

 
$
106,377

 
$
139,384


 
Year Ended December 31,
 
2017
 
2016
 
2015
Percent of pretax income:
 
 
 
 
 
Federal statutory tax
35.0
 %
 
35.0
 %
 
35.0
 %
Tax exempt revenue
(2.4
)
 
(3.1
)
 
(2.2
)
Effect of state income taxes, net of federal benefit
2.0

 
1.9

 
2.1

Utilization of tax credits:
 
 
 
 
 
Low-income housing tax credits, net of amortization
(1.0
)
 
(1.2
)
 
(0.9
)
Other tax credits
(0.3
)
 
(0.6
)
 
(0.5
)
Bank-owned life insurance
(0.6
)
 
(0.9
)
 
(0.7
)
Share-based compensation
(0.5
)
 

 

Revaluation of net deferred tax assets due to change in federal tax rates
1.8

 

 

Write-off of deferred tax assets related to executive compensation
0.4

 

 

Other, net
0.8

 
0.3

 
(0.5
)
Total
35.2
 %
 
31.4
 %
 
32.3
 %


A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):
 
2017
 
2016
 
2015
Balance as of January 1
$
15,841

 
$
13,232

 
$
13,374

Additions for tax for current year positions
4,645

 
5,640

 
2,226

Settlements during the period

 

 

Lapses of applicable statute of limitations
(2,376
)
 
(3,031
)
 
(2,368
)
Balance as of December 31
$
18,110

 
$
15,841

 
$
13,232



Of the above unrecognized tax benefits, $12.2 million, if recognized, would have affected the effective tax rate.

BOK Financial recognizes interest and penalties accrued related to unrecognized tax benefits in income tax expense. The Company recognized $1.2 million for 2017, $1.0 million for 2016 and $1.0 million for 2015 in interest and penalties. The Company had approximately $4.0 million and $3.5 million accrued for the payment of interest and penalties at December 31, 2017 and 2016, respectively. Federal statutes remain open for federal tax returns filed in the previous three reporting periods. Various state income tax statutes remain open for the previous three to six reporting periods.