Investment Securities - Unrealized Loss Position (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized loss position for less than 12 months, Fair Value	$ 144,313	$ 453,336
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss	(161)	(880)
Available-for-sale Securities, Unrealized loss position for more than 12 months, Fair Value	118,044	130,184
Available-for-sale Securities, Unrealized loss position for more than 12 months, Unrealized Loss	(26,900)	(31,347)
Investment Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of securities in unrealized loss position greater than twelve months	8	10
Available-for-sale securities in a loss position for more than 12 months, qualitative disclosure, percent of amortized cost	81.40%
Floating Interest Rate [Member] | Auction-rate certificates backed by Government guaranteed student loans
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized loss position for less than 12 months, Fair Value	0	0
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss	0	0
Available-for-sale Securities, Unrealized loss position for more than 12 months, Fair Value	60,034	60,213
Available-for-sale Securities, Unrealized loss position for more than 12 months, Unrealized Loss	(14,066)	(13,887)
Floating Interest Rate [Member] | Asset-backed Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized loss position for less than 12 months, Fair Value	20,480	63,496
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss	(34)	(102)
Available-for-sale Securities, Unrealized loss position for more than 12 months, Fair Value	0	0
Available-for-sale Securities, Unrealized loss position for more than 12 months, Unrealized Loss	0	0
Floating Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized loss position for less than 12 months, Fair Value	22,715	235,454
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss	(126)	(359)
Available-for-sale Securities, Unrealized loss position for more than 12 months, Fair Value	840	17,409
Available-for-sale Securities, Unrealized loss position for more than 12 months, Unrealized Loss	(4)	(22)
Floating Interest Rate [Member] | Corporate Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized loss position for less than 12 months, Fair Value		41,061
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss		(388)
Available-for-sale Securities, Unrealized loss position for more than 12 months, Fair Value		0
Available-for-sale Securities, Unrealized loss position for more than 12 months, Unrealized Loss		0
Floating Interest Rate [Member] | GSE Subordinated Debt
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized loss position for less than 12 months, Fair Value	0	0
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss	0	0
Available-for-sale Securities, Unrealized loss position for more than 12 months, Fair Value	57,170	52,562
Available-for-sale Securities, Unrealized loss position for more than 12 months, Unrealized Loss	(12,830)	(17,438)
Fixed Interest Rate | Corporate Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized loss position for less than 12 months, Fair Value		18,189
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss		(6)
Available-for-sale Securities, Unrealized loss position for more than 12 months, Fair Value		0
Available-for-sale Securities, Unrealized loss position for more than 12 months, Unrealized Loss		0
Fixed Interest Rate | Senior Agency Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized loss position for less than 12 months, Fair Value		44,976
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss		(21)
Available-for-sale Securities, Unrealized loss position for more than 12 months, Fair Value		0
Available-for-sale Securities, Unrealized loss position for more than 12 months, Unrealized Loss		0
Fixed Interest Rate | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized loss position for less than 12 months, Fair Value	101,118	50,160
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss	(1)	(4)
Available-for-sale Securities, Unrealized loss position for more than 12 months, Fair Value	0	0
Available-for-sale Securities, Unrealized loss position for more than 12 months, Unrealized Loss	$ 0	$ 0