Investment Securities - Schedule of Investment Securities (Details) (USD $)			3 Months Ended		9 Months Ended							0 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Investment Securities [Member]	Sep. 30, 2013 Investment Securities [Member]	Sep. 30, 2014 Investment Securities [Member]	Sep. 30, 2013 Investment Securities [Member]	Dec. 31, 2013 Investment Securities [Member]	Sep. 30, 2014 Senior Agency Debt Securities [Member]	Dec. 31, 2013 Senior Agency Debt Securities [Member]	Sep. 30, 2014 Floating Interest Rate [Member] Floating rate auction-rate certificates backed by Government guaranteed student loans	Dec. 31, 2013 Floating Interest Rate [Member] Floating rate auction-rate certificates backed by Government guaranteed student loans	Sep. 30, 2014 Floating Interest Rate [Member] Asset-backed Securities [Member]	Dec. 31, 2013 Floating Interest Rate [Member] Asset-backed Securities [Member]	Sep. 30, 2014 Floating Interest Rate [Member] Corporate Debt Securities [Member]	Dec. 31, 2013 Floating Interest Rate [Member] Corporate Debt Securities [Member]	Sep. 30, 2014 Floating Interest Rate [Member] Government/GSE Guaranteed Mortgage Backed Securities [Member]	Dec. 31, 2013 Floating Interest Rate [Member] Government/GSE Guaranteed Mortgage Backed Securities [Member]	Sep. 30, 2014 Floating Interest Rate [Member] GSE Subordinated Debt [Member}	Dec. 31, 2013 Floating Interest Rate [Member] GSE Subordinated Debt [Member}	Dec. 31, 2013 Floating Interest Rate [Member] Taxable Municipal Bonds [Member]	Sep. 30, 2014 Floating Interest Rate [Member] US Treasury Securities [Member]	Sep. 30, 2014 Fixed Interest Rate [Member] Corporate Debt Securities [Member]	Dec. 31, 2013 Fixed Interest Rate [Member] Corporate Debt Securities [Member]	Sep. 30, 2014 Fixed Interest Rate [Member] Government/GSE Guaranteed Mortgage Backed Securities [Member]		Dec. 31, 2013 Fixed Interest Rate [Member] Government/GSE Guaranteed Mortgage Backed Securities [Member]	Sep. 30, 2014 Fixed Interest Rate [Member] GSE Preferred Stock [Member]	Dec. 31, 2013 Fixed Interest Rate [Member] GSE Preferred Stock [Member]	Sep. 30, 2014 Fixed Interest Rate [Member] Taxable Municipal Bonds [Member]	Dec. 31, 2013 Fixed Interest Rate [Member] Senior Agency Debt Securities [Member]	Sep. 30, 2014 Fixed Interest Rate [Member] US Treasury Securities [Member]	Dec. 31, 2013 Fixed Interest Rate [Member] US Treasury Securities [Member]	Sep. 30, 2014 Trading Securities [Member] Floating Interest Rate [Member] Asset-backed Securities [Member]	Dec. 31, 2013 Trading Securities [Member] Floating Interest Rate [Member] Asset-backed Securities [Member]	Sep. 30, 2014 Available-for-sale Securities [Member] Investment Securities [Member]	Dec. 31, 2013 Available-for-sale Securities [Member] Investment Securities [Member]	Sep. 30, 2014 Available-for-sale Securities [Member] Floating Interest Rate [Member] Floating rate auction-rate certificates backed by Government guaranteed student loans	Dec. 31, 2013 Available-for-sale Securities [Member] Floating Interest Rate [Member] Floating rate auction-rate certificates backed by Government guaranteed student loans	Sep. 30, 2014 Available-for-sale Securities [Member] Floating Interest Rate [Member] Asset-backed Securities [Member]	Dec. 31, 2013 Available-for-sale Securities [Member] Floating Interest Rate [Member] Asset-backed Securities [Member]	Sep. 30, 2014 Available-for-sale Securities [Member] Floating Interest Rate [Member] Corporate Debt Securities [Member]	Dec. 31, 2013 Available-for-sale Securities [Member] Floating Interest Rate [Member] Corporate Debt Securities [Member]	Sep. 30, 2014 Available-for-sale Securities [Member] Floating Interest Rate [Member] Government/GSE Guaranteed Mortgage Backed Securities [Member]	Dec. 31, 2013 Available-for-sale Securities [Member] Floating Interest Rate [Member] Government/GSE Guaranteed Mortgage Backed Securities [Member]	Sep. 30, 2014 Available-for-sale Securities [Member] Floating Interest Rate [Member] GSE Subordinated Debt [Member}	Dec. 31, 2013 Available-for-sale Securities [Member] Floating Interest Rate [Member] GSE Subordinated Debt [Member}	Dec. 31, 2013 Available-for-sale Securities [Member] Floating Interest Rate [Member] Taxable Municipal Bonds [Member]	Sep. 30, 2014 Available-for-sale Securities [Member] Floating Interest Rate [Member] US Treasury Securities [Member]	Sep. 30, 2014 Available-for-sale Securities [Member] Fixed Interest Rate [Member] Corporate Debt Securities [Member]	Dec. 31, 2013 Available-for-sale Securities [Member] Fixed Interest Rate [Member] Corporate Debt Securities [Member]	Sep. 30, 2014 Available-for-sale Securities [Member] Fixed Interest Rate [Member] Government/GSE Guaranteed Mortgage Backed Securities [Member]	Dec. 31, 2013 Available-for-sale Securities [Member] Fixed Interest Rate [Member] Government/GSE Guaranteed Mortgage Backed Securities [Member]	Sep. 30, 2014 Available-for-sale Securities [Member] Fixed Interest Rate [Member] GSE Preferred Stock [Member]	Dec. 31, 2013 Available-for-sale Securities [Member] Fixed Interest Rate [Member] GSE Preferred Stock [Member]	Sep. 30, 2014 Available-for-sale Securities [Member] Fixed Interest Rate [Member] Taxable Municipal Bonds [Member]	Dec. 31, 2013 Available-for-sale Securities [Member] Fixed Interest Rate [Member] Senior Agency Debt Securities [Member]	Sep. 30, 2014 Available-for-sale Securities [Member] Fixed Interest Rate [Member] US Treasury Securities [Member]	Dec. 31, 2013 Available-for-sale Securities [Member] Fixed Interest Rate [Member] US Treasury Securities [Member]	Sep. 30, 2014 Available-for-sale Securities [Member] Fixed Interest Rate [Member] Interest-Only-Strip [Member]	Dec. 31, 2013 Available-for-sale Securities [Member] Fixed Interest Rate [Member] Interest-Only-Strip [Member]
Available-for-sale Securities [Abstract]
Available-for-Sale Securities Unpaid Principal Balance			$ 1,980,660,000		$ 1,980,660,000		$ 2,475,407,000			$ 46,600,000	$ 74,100,000	$ 108,276,000	$ 166,185,000	$ 10,000,000	$ 109,345,000	$ 627,432,000	$ 612,413,000	$ 70,000,000	$ 70,000,000	$ 30,595,000	$ 75,000,000	$ 30,000,000	$ 55,000,000	$ 892,000		$ 1,173,000	$ 78,500,000	$ 78,500,000	$ 3,960,000	$ 523,691,000	$ 930,000,000	$ 754,405,000
Unamortized Premium/(Discount)			7,717,000		7,717,000		10,014,000																										0	0	7,717,000	10,014,000	0	0	(108,000)	(217,000)	0	(3,000)	3,631,000	4,336,000	0	0	84,000	(12,000)	(16,000)	48,000	3,648,000	3,966,000	17,000	365,000	2,000	294,000	555,000	1,141,000	7,300,000	7,400,000
Available-for-sale Securities, Amortized Cost Basis			1,988,377,000		1,988,377,000		2,485,421,000			46,600,000	74,100,000	108,168,000	165,968,000	10,000,000	109,342,000	631,063,000	616,749,000	70,000,000	70,000,000	30,679,000	74,988,000	29,984,000	55,048,000	4,540,000		5,139,000	78,517,000	78,865,000	3,962,000	523,985,000	930,555,000	755,546,000
Available-for-Sale Gross Unrealized Gains			9,371,000		9,371,000		13,713,000			0	0	181,000	195,000	126,000	445,000	5,054,000	4,955,000	0	0	5,000	27,000	97,000	97,000	3,731,000		3,518,000	0	4,296,000	1,000	107,000	154,000	95,000
Available-for-sale Securities, Unrealized Losses			(12,765,000)		(12,765,000)		(15,987,000)			(5,826,000)	(8,815,000)	(24,000)	(59,000)	0	(18,000)	(279,000)	(435,000)	(6,615,000)	(6,615,000)	(3,000)	0	0	(4,000)	0		0	(17,000)	0	0	(30,000)	(4,000)	(8,000)
Available-for-sale Securities, Fair Value Disclosure			1,984,983,000		1,984,983,000		2,483,147,000	1,687,881,000	1,553,669,000	40,774,000	65,285,000	108,325,000	166,104,000	10,126,000	109,769,000	635,838,000	621,269,000	63,385,000	63,385,000	30,681,000	75,015,000	30,081,000	55,141,000	8,271,000	[1]	8,657,000	78,500,000	83,161,000	3,963,000	524,062,000	930,705,000	755,633,000
Derivative, Notional Amount	6,671,380,000	6,691,851,000																						152,400,000		152,400,000
Proceeds from sale of available-for-sale investment securities			39,700,000	0	770,149,000	170,614,000
Available-for-sale Securities, Gross Realized Gains			100,000		600,000	3,100,000
Trading Securities [Abstract]
Trading Securities - Amount Outstanding												3,012,000	3,553,000
Trading Securities Amortized Cost												3,012,000	3,553,000
Trading Securities, Unrealized Gains												0	0
Trading Securities, Unrealized Losses												(2,235,000)	(2,625,000)
Trading, at fair value			777,000		777,000		928,000	42,964,000	58,344,000			777,000	928,000
Marketable Securities [Abstract]
Marketable Securities Unpaid Principal Balance			1,983,672,000		1,983,672,000		2,478,960,000
Marketable Securities, Amortized Cost			1,991,389,000		1,991,389,000		2,488,974,000
Marketable Securities, Unrealized Gains			9,371,000		9,371,000		13,713,000
Marketable Securities, Unrealized Losses			(15,000,000)		(15,000,000)		(18,612,000)
Marketable Securities			$ 1,985,760,000		$ 1,985,760,000		$ 2,484,075,000	$ 1,730,845,000	$ 1,612,013,000

[1] (1)Fair value includes $7.3 million of an interest-only security with a notional amount of $152.4 million.