Held-to-Maturity Securities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013 position		Dec. 31, 2012 position
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	$ 5,189,118		$ 5,241,312
Other Than Temporarily Impaired Losses, Non Credit Losses, Held-to-maturity Securities	35,293		41,437
Held-to-maturity securities	5,153,825	[1]	5,199,875	[1]
Held To Maturity Securities Accumulated Unrecognized Holding Gain	63,405		84,536
Held To Maturity Securities Accumulated Unrecognized Holding Loss	7,992		446
Held-to-maturity Securities, Fair Value	5,209,238		5,283,965
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions	54		5
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,703,842		27,577
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	7,372		9
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions	43		45
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	280,274		350,622
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	21,987		35,597
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	97		50
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	1,984,116		378,199
Held To Maturity Securities Continuous Unrealized Loss Positon Aggregate Loss	29,359		35,606
US Government Agencies Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	33,373		38,759
Other Than Temporarily Impaired Losses, Non Credit Losses, Held-to-maturity Securities	0		0
Held-to-maturity securities	33,373		38,759
Held To Maturity Securities Accumulated Unrecognized Holding Gain	126		176
Held To Maturity Securities Accumulated Unrecognized Holding Loss	161		175
Held-to-maturity Securities, Fair Value	33,338		38,760
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions	0		0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0		0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0		0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions	2		2
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	16,524		17,874
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	161		175
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	2		2
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	16,524		17,874
Held To Maturity Securities Continuous Unrealized Loss Positon Aggregate Loss	161		175
Held To Maturity Securities Other Than Mortgage Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities	33,373		38,759
Held-to-maturity Securities, Fair Value	33,338		38,760
Held To Maturity Securities Debt Maturities Within One Year Amortized Cost	0		503
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	0		503
Held-to-maturity Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	0		505
Held To Maturity Securities Debt Maturities After One Through Five Years Amortized Cost	16,688		10,331
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	16,688		10,331
Held-to-maturity Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value	16,814		10,423
Held To Maturity Securities Debt Maturities After Five Through Ten Years Amortized Cost	8,483		19,355
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	8,483		19,355
Held-to-maturity Securities, Debt Maturities, Rolling Year Six Through Ten, Fair Value	8,410		19,364
Held To Maturity Securities Debt Maturities After Ten Years Amortized Cost	8,202		8,570
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	8,202		8,570
Held-to-maturity Securities, Debt Maturities, Rolling after Ten Years, Fair Value	8,114		8,468
Held To Maturity Securities Debt Maturities Amortized Cost	33,373		38,759
Mortgage Backed Securities, US Government Guaranteed [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	10,746		12,973
Other Than Temporarily Impaired Losses, Non Credit Losses, Held-to-maturity Securities	0		0
Held-to-maturity securities	10,746		12,973
Held To Maturity Securities Accumulated Unrecognized Holding Gain	50		60
Held To Maturity Securities Accumulated Unrecognized Holding Loss	0		0
Held-to-maturity Securities, Fair Value	10,796		13,033
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	4,936,998		4,947,206
Other Than Temporarily Impaired Losses, Non Credit Losses, Held-to-maturity Securities	0		0
Held-to-maturity securities	4,936,998		4,947,206
Held To Maturity Securities Accumulated Unrecognized Holding Gain	48,991		78,023
Held To Maturity Securities Accumulated Unrecognized Holding Loss	7,831		271
Held-to-maturity Securities, Fair Value	4,978,158		5,024,958
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions	54		5
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,703,842		27,577
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	7,372		9
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions	12		13
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	93,651		125,534
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	459		262
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	66		18
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	1,797,493		153,111
Held To Maturity Securities Continuous Unrealized Loss Positon Aggregate Loss	7,831		271
Private Label Residential Mortgage Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	208,001		242,374
Other Than Temporarily Impaired Losses, Non Credit Losses, Held-to-maturity Securities	35,293		41,437
Held-to-maturity securities	172,708		200,937
Held To Maturity Securities Accumulated Unrecognized Holding Gain	14,238		6,277
Held To Maturity Securities Accumulated Unrecognized Holding Loss	0		0
Held-to-maturity Securities, Fair Value	186,946		207,214
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions	0		0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0		0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0		0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions	29		30
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	170,099		207,214
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	21,367		35,160
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	29		30
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	170,099		207,214
Held To Maturity Securities Continuous Unrealized Loss Positon Aggregate Loss	21,367		35,160
Collateralized Mortgage Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	5,155,745		5,202,553
Other Than Temporarily Impaired Losses, Non Credit Losses, Held-to-maturity Securities	35,293		41,437
Held-to-maturity securities	5,120,452		5,161,116
Held To Maturity Securities Accumulated Unrecognized Holding Gain	63,279		84,360
Held To Maturity Securities Accumulated Unrecognized Holding Loss	7,831		271
Held-to-maturity Securities, Fair Value	5,175,900		5,245,205
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions	54		5
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,703,842		27,577
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	7,372		9
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions	41		43
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	263,750		332,748
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	21,826		35,422
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	95		48
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	1,967,592		360,325
Held To Maturity Securities Continuous Unrealized Loss Positon Aggregate Loss	29,198		35,431
Held-to-maturity Securities, Premium (Discounts), Net	(38,439)		(52,608)
US Treasury and Government [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held To Maturity Securities Continuous Unrealized Loss Positon Aggregate Loss	$ 7,992

[1] (a)Fair values: $5,209,238 and $5,283,965 at September 30, 2013 and December 31, 2012, respectively.