Income Taxes - Components of Company's Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Allowance for loan losses	$ 72,940	$ 57,667
Employee compensation and benefits	26,853	50,361
Loan purchase accounting adjustments	18,977	35,094
Tax credit carryforward	42,850	35,553
Securities	5,038
State net operating loss	1,910	1,535
Other	10,928	8,472
Gross deferred tax assets	179,496	188,682
State valuation allowance	(1,910)	(1,529)
Subtotal valuation allowance	(1,910)	(1,529)
Net deferred tax assets	177,586	187,153
Deferred tax liabilities:
Fixed assets & intangibles	(80,389)	(88,062)
Securities		(724)
FDIC indemnification asset	(10,688)	(18,769)
Other	(10,679)	(5,263)
Gross deferred tax liabilities	(101,756)	(112,818)
Net deferred tax asset	$ 75,830	$ 74,335