Derivative Financial Instruments - Schedule of Amounts Related to Interest Rate Derivatives Included in Income Designated as Hedges of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Designated as Hedging Instrument [Member] Junior Subordinated Deferred Interest Debentures [Member]	Sep. 30, 2012 Designated as Hedging Instrument [Member] Junior Subordinated Deferred Interest Debentures [Member]	Sep. 30, 2013 Designated as Hedging Instrument [Member] Junior Subordinated Deferred Interest Debentures [Member]	Sep. 30, 2012 Designated as Hedging Instrument [Member] Junior Subordinated Deferred Interest Debentures [Member]	Sep. 30, 2013 Designated as Hedging Instrument [Member] Interest Income on Loans [Member] Interest Rate Swaps/Caps/Floors on Variable-Rate Loans [Member]	Sep. 30, 2012 Designated as Hedging Instrument [Member] Interest Income on Loans [Member] Interest Rate Swaps/Caps/Floors on Variable-Rate Loans [Member]	Sep. 30, 2013 Designated as Hedging Instrument [Member] Interest Income on Loans [Member] Interest Rate Swaps/Caps/Floors on Variable-Rate Loans [Member]	Sep. 30, 2012 Designated as Hedging Instrument [Member] Interest Income on Loans [Member] Interest Rate Swaps/Caps/Floors on Variable-Rate Loans [Member]	Sep. 30, 2013 Designated as Hedging Instrument [Member] Interest Expense [Member] Junior Subordinated Deferred Interest Debentures [Member]	Sep. 30, 2012 Designated as Hedging Instrument [Member] Interest Expense [Member] Junior Subordinated Deferred Interest Debentures [Member]	Sep. 30, 2013 Designated as Hedging Instrument [Member] Interest Expense [Member] Junior Subordinated Deferred Interest Debentures [Member]	Sep. 30, 2012 Designated as Hedging Instrument [Member] Interest Expense [Member] Junior Subordinated Deferred Interest Debentures [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount reclassified from accumulated other comprehensive income to interest income on loans							$ 9,345	$ 9,345	$ 28,035	$ 28,035	$ 1,120	$ 1,063	$ 3,308	$ 3,140
Amount of gain (loss) recognized in other comprehensive income	$ 26,000	$ 44,200	$ (15)	$ (269)	$ (48)	$ (760)