Income Taxes - Components of Company's Deferred Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets:
Allowance for loan losses	$ 77,957	$ 85,289
Employee compensation and benefits	64,030	40,013
Loan purchase accounting adjustments	185,789	241,412
Tax credit carryforward	35,605	25,465
Federal net operating loss		24,524
State net operating loss	1,805	2,958
Other	18,102	25,436
Gross deferred tax assets	383,288	445,097
Federal valuation allowance
State valuation allowance	(1,805)	(2,415)
Subtotal valuation allowance	(1,805)	(2,415)
Net deferred tax assets	381,483	442,682
Deferred tax liabilities:
Fixed assets & intangibles	(124,402)	(135,987)
Securities	(46,088)	(55,642)
Deferred gain on acquisition	(8,962)	(13,232)
FDIC loss share receivable	(62,311)	(83,348)
Other	(11,335)	(8,713)
Gross deferred tax liabilities	(253,098)	(296,922)
Net deferred tax asset (liability)	$ 128,385	$ 145,760