Income Taxes - Summary of Income Tax Reconciliation (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Federal income tax at expected statutory rate									$ 62,629	$ 73,631	$ 68,326
Tax-exempt interest, net of interest incurred to carry tax-exempt securities									(4,876)	(4,478)	(3,736)
Bank owned life insurance									(2,087)	(2,399)	(2,583)
State income tax expense, net of federal tax effect									9,904	8,204	12,727
Tax credits									(17,408)	(10,070)	(12,760)
Other, net									(1,183)	1,860	732
Income tax expense	$ 16,061	$ 7,143	$ 10,961	$ 12,814	$ 14,702	$ 22,402	$ 14,366	$ 15,278	$ 46,979	$ 66,748	$ 62,706