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	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in other comprehensive income	$ 44,200	$ 68,500
Designated as Hedging Instrument [Member] | Interest Rate Swaps On Variable-Rate Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in other comprehensive income			68,865
Designated as Hedging Instrument [Member] | Junior Subordinated Deferred Interest Debentures [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in other comprehensive income	(783)	(2,321)	(7,312)
Designated as Hedging Instrument [Member] | Interest Income on Loans [Member] | Interest Rate Swaps On Variable-Rate Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount reclassified from accumulated other comprehensive income	37,380	37,380	43,389
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	$ 4,224	$ 4,386	$ 4,367