Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of components of income tax expenses

The following table presents the components of income tax expense for the years indicated:

($ in thousands)	Year Ended December 31,
	2017			2016			2015
Current income tax expense (benefit):
Federal	$	120,968		$	63,642		$	(62,829	)
State	72,837			48,558			(4,750		)
Foreign	1,815			1,345			409
Total current income tax expense (benefit)	195,620			113,545			(67,170		)
Deferred income tax expense (benefit):
Federal	40,057			25,296			199,858
State	(6,201		)	1,883			60,437
Foreign	—			(213		)	919
Total deferred income tax expense	33,856			26,966			261,214
Income tax expense	$	229,476		$	140,511		$	194,044

Schedule of reconciliation of the federal statutory rate to the effective income tax rate

The following table presents the reconciliation of the federal statutory rate to the Company’s effective tax rate for the years ended December 31,2017, 2016 and 2015:

	Year Ended December 31,
	2017		2016		2015
Federal income tax provision at statutory rate	35.0	%	35.0	%	35.0	%
State franchise taxes, net of federal tax effect	5.9		6.1		6.3
Tax Cuts and Jobs Act of 2017 (the “Tax Act”)	4.5		—		—
Tax credits, net of amortization	(15.1	)	(18.3	)	(8.7	)
Other, net	0.9		1.8		0.9
Effective tax rate	31.2	%	24.6	%	33.5	%

Schedule of tax effects of temporary differences that give rise to significant portions of the deferred tax assets (liabilities)

The tax effects of temporary differences that give rise to a significant portion of deferred tax assets and deferred tax liabilities as of December 31, 2017 and 2016 are presented below:

($ in thousands)	December 31,
	2017												2016
	Federal			State			Foreign			Total			Federal			State			Foreign			Total
Deferred tax assets:
Allowance for loan losses and OREO reserves	$	62,942		$	28,857		$	1,365		$	93,164		$	97,921		$	27,792		$	1,365		$	127,078
Deferred compensation	11,483			5,220			—			16,703			20,093			5,731			—			25,824
Mortgage servicing assets	2,727			1,206			—			3,933			—			—			—			—
Unrealized losses on securities	10,730			5,354			—			16,084			16,253			5,315			—			21,568
State taxes	5,217			—			—			5,217			1,333			—			—			1,333
Interest income on nonaccrual loans	5,396			2,451			—			7,847			4,461			1,258			—			5,719
Other, net	744			5,481			97			6,322			2,053			5,269			97			7,419
Total gross deferred tax assets	99,239			48,569			1,462			149,270			142,114			45,365			1,462			188,941
Valuation allowance	—			(256		)	—			(256		)	—			(283		)	—			(283		)
Total deferred tax assets, net of valuation allowance	$	99,239		$	48,313		$	1,462		$	149,014		$	142,114		$	45,082		$	1,462		$	188,658
Deferred tax liabilities:
Core deposit intangibles	$	(4,408	)	$	(2,117	)	$	—		$	(6,525	)	$	(9,768	)	$	(2,874	)	$	—		$	(12,642	)
Investments in partnerships, tax credit and other investments, net	(10,838		)	7,025			—			(3,813		)	(7,012		)	5,318			—			(1,694		)
Fixed assets	(2,671		)	914			—			(1,757		)	(13,166		)	(3,360		)	—			(16,526		)
Equipment financing	(21,844		)	(3,760		)	—			(25,604		)	(13,240		)	(1,866		)	—			(15,106		)
FHLB stock dividends	(1,285		)	(583		)	—			(1,868		)	(1,189		)	(335		)	—			(1,524		)
Acquired debt	(1,273		)	(578		)	—			(1,851		)	(2,210		)	(623		)	—			(2,833		)
Acquired loans and OREO	(2,252		)	(754		)	(406		)	(3,412		)	(5,407		)	(1,242		)	(406		)	(7,055		)
Prepaid expenses	(4,142		)	(1,517		)	—			(5,659		)	(1,088		)	(251		)	—			(1,339		)
Other, net	(510		)	(609		)	—			(1,119		)	(121		)	(120		)	—			(241		)
Total gross deferred tax liabilities	$	(49,223	)	$	(1,979	)	$	(406	)	$	(51,608	)	$	(53,201	)	$	(5,353	)	$	(406	)	$	(58,960	)
Net deferred tax assets	$	50,016		$	46,334		$	1,056		$	97,406		$	88,913		$	39,729		$	1,056		$	129,698

Summary of the activity related to unrecognized tax benefits

The following table summarizes the activities related to the Company’s unrecognized tax benefits as of the periods indicated:

($ in thousands)	Year Ended December 31,
	2017		2016
Beginning Balance	$	10,419	$	7,125
Additions for tax positions related to prior years	—		5,819
Settlements with taxing authorities	—		(2,525		)
Ending Balance	$	10,419	$	10,419