Investment Securities - Unrealized Loss Position (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized loss position for less than 12 months, Fair Value	$ 36,265	$ 382,282
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss	(23)	(246)
Available-for-sale Securities, Unrealized loss position for more than 12 months, Fair Value	139,517	125,038
Available-for-sale Securities, Unrealized loss position for more than 12 months, Unrealized Loss	(15,749)	(23,521)
Investment Securities [Member]
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	9	9
Available-for-sale securities in a loss position for more than 12 months, qualitative disclosure, percent of amortized cost	89.90%
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	65,213	63,159
Available-for-sale Securities, Unrealized loss position for more than 12 months, Unrealized Loss	(8,887)	(10,941)
Floating Interest Rate [Member] | Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized loss position for less than 12 months, Fair Value	0	21,648
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss	0	(27)
Available-for-sale Securities, Unrealized loss position for more than 12 months, Fair Value	10,337	3,619
Available-for-sale Securities, Unrealized loss position for more than 12 months, Unrealized Loss	(11)	(9)
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	8,185	174,352
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss	(2)	(209)
Available-for-sale Securities, Unrealized loss position for more than 12 months, Fair Value	816	829
Available-for-sale Securities, Unrealized loss position for more than 12 months, Unrealized Loss	(2)	(2)
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	63,151	57,431
Available-for-sale Securities, Unrealized loss position for more than 12 months, Unrealized Loss	(6,849)	(12,569)
Fixed Interest Rate [Member] | Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Unrealized loss position for less than 12 months, Fair Value	2,981
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss	(3)
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 [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	25,099
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss	(18)
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 [Member] | 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		50,088
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss		(1)
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 [Member] | 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		136,194
Available-for-sale Securities, Unrealized loss position for less than 12 months, Unrealized Loss		(9)
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