Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Current and Deferred Income Tax Expense (Benefit)

The current and deferred amounts of income tax expense (benefit) were as follows.



	Years Ended December 31,
	2017		2016		2015
	($ in Thousands)
Current
Federal	$	76,525	$	73,781	$	82,449
State	11,576		2,885		2,560
Total current	88,101		76,666		85,009
Deferred
Federal	19,755		3,338		(10,606		)
State	1,647		7,318		7,084
Total deferred	21,402		10,656		(3,522		)
Total income tax expense	$	109,503	$	87,322	$	81,487

Schedule of Deferred Tax Assets and Liabilities

Temporary differences between the amounts reported in the financial statements and the tax bases of assets and liabilities resulted in deferred taxes. Deferred tax assets and liabilities at December 31 were as follows.



	2017			2016
	($ in Thousands)
Deferred tax assets
Allowance for loan losses	$	66,377		$	100,891
Allowance for other losses	7,095			11,080
Accrued liabilities	3,884			5,969
Deferred compensation	20,015			33,169
Benefit of tax loss and credit carryforwards	8,438			7,882
Nonaccrual interest	1,619			1,085
Net unrealized losses on available-for-sale securities	15,968			16,980
Net unrealized losses on pension and postretirement benefits	9,928			21,218
Other	3,954			8,128
Total deferred tax assets	137,278			206,402
Valuation allowance for deferred tax assets	(269		)	—
Total deferred tax assets after valuation allowance	137,009			206,402

Deferred tax liabilities
Prepaid expenses	49,695			70,943
Goodwill	19,144			27,365
Mortgage banking activities	10,949			17,569
Deferred loan fee income	11,467			16,474
State deferred taxes	2,001			3,800
Lease financing	535			1,975
Bank premises and equipment	5,063			7,698
Other	4,838			8,594
Total deferred tax liabilities	103,692			154,418
Net deferred tax assets	$	33,317		$	51,984

Summary of Valuation Allowance [Table Text Block]

At December 31, 2017 the valuation allowance for deferred tax assets of approximately $269,000 was related to the deferred tax benefit of specific federal tax loss carryforwards of $3 million from the acquisition of Whitnell & Co. in 2017.



	2017		2016
	($ in Thousands)
Valuation allowance for deferred tax assets, beginning of year	$	—	$	—
Increase (decrease) in current year	269		—
Valuation allowance for deferred tax assets, end of year	$	269	$	—

Schedule of Effective Income Tax Rate Reconciliation

The effective income tax rate differs from the statutory federal tax rate. The major reasons for this difference were as follows.



	2017		2016		2015
Federal income tax rate at statutory rate	35.0	%	35.0	%	35.0	%
Increases (decreases) resulting from:
Tax-exempt interest and dividends	(4.1	)%	(4.8	)%	(5.0	)%
State income taxes (net of federal benefit)	2.7	%	2.3	%	2.3	%
Bank owned life insurance	(1.7	)%	(1.7	)%	(1.2	)%
Tax effect of tax credits and benefits, net of related expenses	(0.5	)%	(0.8	)%	(0.5	)%
Tax reserve adjustments	(1.2	)%	0.3	%	(0.6	)%
Net tax benefit from stock-based compensation	(1.3	)%	(0.4	)%	—	%
Tax Cuts and Jobs Act impact on deferred remeasurement	3.5	%	—	%	—	%
Other	(0.1	)%	0.5	%	0.2	%
Effective income tax rate	32.3	%	30.4	%	30.2	%

Summary Unrecognized Tax Benefits

A reconciliation of the beginning and ending amount of unrecognized tax benefits was as follows.



	2017			2016
	($ in Millions)
Balance at beginning of year	$	10		$	9
Subtractions for tax positions related to prior years	(5		)	—
Subtractions for settlements with tax authorities	(1		)	—
Additions for tax positions related to current year	—			1
Balance at end of year	$	4		$	10