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, 2014	Dec. 31, 2013	Sep. 30, 2014 Designated as Hedging Instrument [Member] Interest rate swap on junior subordinated deferrable interest debentures [Member]	Sep. 30, 2013 Designated as Hedging Instrument [Member] Interest rate swap on junior subordinated deferrable interest debentures [Member]	Sep. 30, 2014 Designated as Hedging Instrument [Member] Interest rate swap on junior subordinated deferrable interest debentures [Member]	Sep. 30, 2013 Designated as Hedging Instrument [Member] Interest rate swap on junior subordinated deferrable interest debentures [Member]	Sep. 30, 2014 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, 2014 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, 2014 Designated as Hedging Instrument [Member] Interest Expense [Member] Interest rate swap on junior subordinated deferrable interest debentures [Member]	Sep. 30, 2013 Designated as Hedging Instrument [Member] Interest Expense [Member] Interest rate swap on junior subordinated deferrable interest debentures [Member]	Sep. 30, 2014 Designated as Hedging Instrument [Member] Interest Expense [Member] Interest rate swap on junior subordinated deferrable interest debentures [Member]	Sep. 30, 2013 Designated as Hedging Instrument [Member] Interest Expense [Member] Interest rate swap on junior subordinated deferrable interest debentures [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount reclassified from accumulated other comprehensive income to interest							$ 9,345	$ 9,345	$ 28,035	$ 28,035	$ 0	$ 1,120	$ 0	$ 3,308
Amount of gain (loss) recognized in other comprehensive income	$ 1,700	$ 19,900	$ 0	$ (15)	$ 0	$ (48)