Investment Securities - Unrealized Loss Position (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014 position	Dec. 31, 2013 position
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 788,252	$ 684,499
Available-for-Sale Continuous Unrealized Loss Position Less than 12 Months, Aggregate Losses	333	557
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	127,897	128,670
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(13,250)	(15,430)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	33	64
Investment Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions In Loss Position Greater than Twelve Months	10	7
Available-for-Sale Securities Gross Unrealized Losses	13,583	15,987
Available-for-sale securities in a loss position for more than 12 months, qualitative disclosure, percent of amortized cost	90.60%
Standard & Poor's, A- Rating [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	1	2
Standard & Poor's, BBB+ Rating [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		1
Floating Interest Rate [Member] | Auction-rate certificates backed by Government guaranteed student loans [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	0
Available-for-Sale Continuous Unrealized Loss Position Less than 12 Months, Aggregate Losses	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	54,976	65,285
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(6,624)	(8,815)
Available-for-Sale Securities Gross Unrealized Losses	6,624	8,815
Floating Interest Rate [Member] | Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	6,102	50,129
Available-for-Sale Continuous Unrealized Loss Position Less than 12 Months, Aggregate Losses	4	59
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,676	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(1)	0
Available-for-Sale Securities Gross Unrealized Losses	4	59
Floating Interest Rate [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		19,982
Available-for-Sale Continuous Unrealized Loss Position Less than 12 Months, Aggregate Losses		18
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		0
Available-for-Sale Securities Gross Unrealized Losses	0	18
Floating Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	204,085	161,960
Available-for-Sale Continuous Unrealized Loss Position Less than 12 Months, Aggregate Losses	252	435
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	6,860	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(10)	0
Available-for-Sale Securities Gross Unrealized Losses	262	435
Floating Interest Rate [Member] | GSE Subordinated Debt [Member}
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	0
Available-for-Sale Continuous Unrealized Loss Position Less than 12 Months, Aggregate Losses	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	63,385	63,385
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(6,615)	(6,615)
Available-for-Sale Securities Gross Unrealized Losses	6,615	6,615
Floating Interest Rate [Member] | Taxable Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities Gross Unrealized Losses		3
Floating Interest Rate [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities Gross Unrealized Losses	0
Fixed Interest Rate [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		10,058
Available-for-Sale Continuous Unrealized Loss Position Less than 12 Months, Aggregate Losses		4
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		0
Available-for-Sale Securities Gross Unrealized Losses	0	4
Fixed Interest Rate [Member] | Government/GSE Guaranteed Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities Gross Unrealized Losses	0	0
Fixed Interest Rate [Member] | Taxable Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		8,041
Available-for-Sale Continuous Unrealized Loss Position Less than 12 Months, Aggregate Losses		3
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		0
Available-for-Sale Securities Gross Unrealized Losses	0
Fixed Interest Rate [Member] | Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities Gross Unrealized Losses	0	0
Fixed Interest Rate [Member] | Senior Agency Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		316,273
Available-for-Sale Continuous Unrealized Loss Position Less than 12 Months, Aggregate Losses		30
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		0
Available-for-Sale Securities Gross Unrealized Losses	0	30
Fixed Interest Rate [Member] | US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	578,065	118,056
Available-for-Sale Continuous Unrealized Loss Position Less than 12 Months, Aggregate Losses	77	8
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0	0
Available-for-Sale Securities Gross Unrealized Losses	$ 78	$ 8