Investment Securities - Schedule of Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	0 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Schedule of Available-for-sale and Trading Securities [Line Items]
Derivative, Notional Amount	$ 6,628,072		$ 6,691,851
Investment Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-Sale Securities Unpaid Principal Balance	2,464,198		2,475,407
Debt Instrument, Unamortized Discount (Premium), Net	8,870		10,014
Available-for-sale Securities, Amortized Cost Basis	2,473,068		2,485,421
Available-for-Sale Gross Unrealized Gains	12,589		13,713
Available-for-sale Securities, Unrealized Losses	(16,565)		(15,987)
Available-for-sale Securities, Fair Value Disclosure	2,469,092		2,483,147
Trading, at fair value	923		928
Marketable Securities Unpaid Principal Balance	2,467,468		2,478,960
Marketable Securities, Amortized Cost	2,476,338		2,488,974
Marketable Securities, Unrealized Gains	12,589		13,713
Marketable Securities, Unrealized Losses	(18,912)		(18,612)
Marketable Securities	2,470,015		2,484,075
Available-for-sale Securities [Member] | Investment Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	8,870		10,014
Floating Interest Rate [Member] | Auction-rate certificates backed by Government guaranteed student loans [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-Sale Securities Unpaid Principal Balance	74,100		74,100
Available-for-sale Securities, Amortized Cost Basis	74,100		74,100
Available-for-Sale Gross Unrealized Gains	0		0
Available-for-sale Securities, Unrealized Losses	(9,137)		(8,815)
Available-for-sale Securities, Fair Value Disclosure	64,963		65,285
Floating Interest Rate [Member] | Asset-backed Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-Sale Securities Unpaid Principal Balance	177,999		166,185
Available-for-sale Securities, Amortized Cost Basis	177,823		165,968
Available-for-Sale Gross Unrealized Gains	385		195
Available-for-sale Securities, Unrealized Losses	(13)		(59)
Available-for-sale Securities, Fair Value Disclosure	178,195		166,104
Trading Securities - Amount Outstanding	3,270		3,553
Trading Securities Amortized Cost	3,270		3,553
Trading Securities, Unrealized Gains	0		0
Trading Securities, Unrealized Losses	(2,347)		(2,625)
Trading, at fair value	923		928
Floating Interest Rate [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-Sale Securities Unpaid Principal Balance	107,130		109,345
Available-for-sale Securities, Amortized Cost Basis	107,132		109,342
Available-for-Sale Gross Unrealized Gains	411		445
Available-for-sale Securities, Unrealized Losses	(1)		(18)
Available-for-sale Securities, Fair Value Disclosure	107,542		109,769
Floating Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-Sale Securities Unpaid Principal Balance	640,910		612,413
Available-for-sale Securities, Amortized Cost Basis	644,966		616,749
Available-for-Sale Gross Unrealized Gains	4,891		4,955
Available-for-sale Securities, Unrealized Losses	(640)		(435)
Available-for-sale Securities, Fair Value Disclosure	649,217		621,269
Floating Interest Rate [Member] | GSE Subordinated Debt [Member}
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-Sale Securities Unpaid Principal Balance	70,000		70,000
Available-for-sale Securities, Amortized Cost Basis	70,000		70,000
Available-for-Sale Gross Unrealized Gains	0		0
Available-for-sale Securities, Unrealized Losses	(6,615)		(6,615)
Available-for-sale Securities, Fair Value Disclosure	63,385		63,385
Floating Interest Rate [Member] | Taxable Municipal Bonds [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-Sale Securities Unpaid Principal Balance			30,595
Available-for-sale Securities, Amortized Cost Basis			30,679
Available-for-Sale Gross Unrealized Gains			5
Available-for-sale Securities, Unrealized Losses			(3)
Available-for-sale Securities, Fair Value Disclosure			30,681
Floating Interest Rate [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-Sale Securities Unpaid Principal Balance	75,000
Available-for-sale Securities, Amortized Cost Basis	74,984
Available-for-Sale Gross Unrealized Gains	0
Available-for-sale Securities, Unrealized Losses	(26)
Available-for-sale Securities, Fair Value Disclosure	74,958
Floating Interest Rate [Member] | Available-for-sale Securities [Member] | Auction-rate certificates backed by Government guaranteed student loans [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	0		0
Floating Interest Rate [Member] | Available-for-sale Securities [Member] | Asset-backed Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	(176)		(217)
Floating Interest Rate [Member] | Available-for-sale Securities [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	2		(3)
Floating Interest Rate [Member] | Available-for-sale Securities [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	4,056		4,336
Floating Interest Rate [Member] | Available-for-sale Securities [Member] | GSE Subordinated Debt [Member}
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	0		0
Floating Interest Rate [Member] | Available-for-sale Securities [Member] | Taxable Municipal Bonds [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net			84
Floating Interest Rate [Member] | Available-for-sale Securities [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	(16)
Floating Interest Rate [Member] | Trading Account Assets [Member] | Asset-backed Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	0		0
Fixed Interest Rate [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-Sale Securities Unpaid Principal Balance	55,000		55,000
Available-for-sale Securities, Amortized Cost Basis	55,032		55,048
Available-for-Sale Gross Unrealized Gains	158		97
Available-for-sale Securities, Unrealized Losses	0		(4)
Available-for-sale Securities, Fair Value Disclosure	55,190		55,141
Fixed Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-Sale Securities Unpaid Principal Balance	1,123		1,173
Available-for-sale Securities, Amortized Cost Basis	4,983		5,139
Available-for-Sale Gross Unrealized Gains	3,601		3,518
Available-for-sale Securities, Unrealized Losses	0		0
Available-for-sale Securities, Fair Value Disclosure	8,584	[1]	8,657
Derivative, Notional Amount	152,400		152,400
Fixed Interest Rate [Member] | GSE Preferred Stock [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-Sale Securities Unpaid Principal Balance	78,500		78,500
Available-for-sale Securities, Amortized Cost Basis	78,753		78,865
Available-for-Sale Gross Unrealized Gains	2,887		4,296
Available-for-sale Securities, Unrealized Losses	0		0
Available-for-sale Securities, Fair Value Disclosure	81,640		83,161
Fixed Interest Rate [Member] | Taxable Municipal Bonds [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-Sale Securities Unpaid Principal Balance	22,053
Available-for-sale Securities, Amortized Cost Basis	22,100
Available-for-Sale Gross Unrealized Gains	7
Available-for-sale Securities, Unrealized Losses	0
Available-for-sale Securities, Fair Value Disclosure	22,107
Fixed Interest Rate [Member] | Senior Agency Debt Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-Sale Securities Unpaid Principal Balance	518,691		523,691
Available-for-sale Securities, Amortized Cost Basis	518,895		523,985
Available-for-Sale Gross Unrealized Gains	149		107
Available-for-sale Securities, Unrealized Losses	(129)		(30)
Available-for-sale Securities, Fair Value Disclosure	518,915		524,062
Fixed Interest Rate [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-Sale Securities Unpaid Principal Balance	643,692		754,405
Available-for-sale Securities, Amortized Cost Basis	644,300		755,546
Available-for-Sale Gross Unrealized Gains	100		95
Available-for-sale Securities, Unrealized Losses	(4)		(8)
Available-for-sale Securities, Fair Value Disclosure	644,396		755,633
Fixed Interest Rate [Member] | Available-for-sale Securities [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	32		48
Fixed Interest Rate [Member] | Available-for-sale Securities [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	3,860		3,966
Fixed Interest Rate [Member] | Available-for-sale Securities [Member] | GSE Preferred Stock [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	253		365
Fixed Interest Rate [Member] | Available-for-sale Securities [Member] | Taxable Municipal Bonds [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	47
Fixed Interest Rate [Member] | Available-for-sale Securities [Member] | Senior Agency Debt Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	204		294
Fixed Interest Rate [Member] | Available-for-sale Securities [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	608		1,141
Fixed Interest Rate [Member] | Available-for-sale Securities [Member] | Interest-Only-Strip [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	$ 7,400		$ 7,400

[1] (1)Fair value includes $7.4 million of an interest-only security with a notional amount of $152.4 million.