Derivative Financial Instruments (Narrative) (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Amount reclassified from accumulated other comprehensive income to interest expense			$ 6,100,000
Fair value hedges, interest rate with notional amount	96,500,000		96,500,000
Fair value hedges recognized interest income	50,000
Mortgage loans held-for-sale	570,000,000		570,000,000
Fair value hedges foreign currency derivatives notional amount	5,000,000		5,000,000
Fair value hedges non-designated notional amount	508,500,000		508,500,000
Fair value of interest rate derivatives in a net liability position	58,900,000		58,900,000
Cash collateral	7,100,000		7,100,000
Collateral securities	48,700,000		48,700,000
Cash Flow Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate swaps, aggregate notional amount	225,000,000		225,000,000
Interest Rate Swaps And Caps [Member] | Cash Flow Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate swaps, aggregate notional amount	225,000,000		225,000,000
Interest Rate Contract [Member] | Other Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Income Statement Gain/(Loss) due to Hedge Ineffectiveness	37,000	0	50,000	0
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Aggregate notional amount	2,000,000,000		2,000,000,000
Forward Commitments To Sell Mortgage Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Aggregate notional amount	1,200,000,000		1,200,000,000
Interest Rate Lock Commitments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Aggregate notional amount	588,800,000		588,800,000
Call Options Written [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Net	$ 0	$ 0	$ 0	$ 0