Financial Derivatives Schedule of Derivative Instruments, Gain(Loss) in Statement of Financial Performance (Details) (USD $)	3 Months Ended							12 Months Ended						15 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010		Sep. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
amortization of derivatives transition adjustment								$ 0		$ 0		$ (70,000)
Gain (loss) on derivatives instruments and hedging activity net pretax	3,505,000	1,558,000	(31,292,000)	6,400,000	(10,277,000)	(17,806,000)	4,005,000	(19,829,000)		(92,645,000)		(17,159,000)		(68,567,000)
Non-Interest Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives instruments and hedging activity net pretax								(19,829,000)		(92,645,000)		(17,159,000)
Non-Interest Income [Member] | Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge								6,388,000		0		0
Gain (Loss) on Fair Value Hedges Recognized in Earnings								5,984,000	[1]	0	[1]	0	[1]
Non-Interest Income [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax								(25,813,000)		(92,645,000)		(17,089,000)
Interest Rate Swap [Member] | Non-Interest Income [Member] | Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Components Excluded from Assessment of Interest Rate Fair Value Hedge Effectiveness								5,900,000
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments								(404,000)		0		0
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net								100,000
Interest Rate Swap [Member] | Non-Interest Income [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax								(24,763,000)		(86,402,000)		(13,071,000)
Agency Forward [Member] | Non-Interest Income [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax								(828,000)		(5,710,000)		(3,246,000)
Treasury Futures [Member] | Non-Interest Income [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax								(129,000)		(513,000)		(465,000)
Credit Default Swap [Member] | Non-Interest Income [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax								$ (93,000)		$ (20,000)		$ (307,000)

[1] ludes gains of $5.9 million that are excluded from the assessment of hedge effectiveness as they relate to the amortization of the fair value of the hedged items prior to hedge inception, and gains of $0.1 million due to hedge ineffectiveness for the year en