Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income tax expense was as follows:



	2017			2016			2015
Current income tax expense	$	58,707		$	48,748		$	59,530
Deferred income tax expense (benefit)	(14,493		)	(11,598		)	(19,059		)
Income tax expense, as reported	$	44,214		$	37,150		$	40,471

Effective tax rate	10.8		%	10.9		%	12.7		%

Income Tax Computed by Applying U.S. Federal Statutory Income Tax Rate

A reconciliation between reported income tax expense and the amounts computed by applying the U.S. federal statutory income tax rate of 35% to income before income taxes is presented in the following table.



	2017			2016			2015
Income tax expense computed at the statutory rate	$	142,927		$	119,494		$	111,930
Effect of tax-exempt interest	(81,995		)	(75,696		)	(70,889		)
Bank owned life insurance income	(1,116		)	(1,260		)	(1,255		)
Net tax benefit from stock-based compensation	(9,062		)	(5,063		)	—
Provisional deferred tax adjustment related to reduction in U.S. federal statutory income tax rate	(4,047		)	—			—
Correction for prior year tax-exempt interest	(2,906		)	—			—
Other	413			(325		)	685
Income tax expense, as reported	$	44,214		$	37,150		$	40,471

Schedule of Deferred Tax Assets and Liabilities

Year-end deferred taxes are presented in the table below. As a result of the Tax Cuts and Jobs Act enacted on December 22, 2017 (discussed below), deferred taxes as of December 31, 2017 are based on the newly enacted U.S. statutory federal income tax rate of 21%. Deferred taxes as of December 31, 2016 are based on the previously enacted U.S. statutory federal income tax rate of 35%.



	2017			2016
Deferred tax assets:
Allowance for loan losses	$	32,626		$	53,566
Alternative minimum tax carryforward, no expiration date	47,104			30,384
Net actuarial loss on defined benefit post-retirement benefit plans	12,160			21,956
Stock-based compensation	9,904			18,140
Bonus accrual	1,136			7,035
Gain on sale of assets	883			2,485
Transaction costs	875			1,587
Other	3,996			4,449
Total gross deferred tax assets	108,684			139,602
Deferred tax liabilities:
Premises and equipment	(20,236		)	(33,777		)
Defined benefit post-retirement benefit plans	(9,012		)	(14,828		)
Intangible assets	(9,014		)	(11,697		)
Net unrealized gain on securities available for sale and transferred securities	(35,829		)	(8,699		)
Leases	(1,646		)	(3,042		)
Section 481(a) change in accounting method (tangible property)	—			(1,694		)
Prepaid expenses	(996		)	(1,743		)
Other	(233		)	(436		)
Total gross deferred tax liabilities	(76,966		)	(75,916		)
Net deferred tax asset (liability)	$	31,718		$	63,686