Investment Securities AFS Gross Unrealized Losses (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	$ (3,189)	$ (82,852)
Unrealized losses on available for sale securities, 12 months or more	(53,343)	(25,182)
Total unrealized losses on available for sale securities	(56,532)	(108,034)
Fair value of unrealized losses on available for sale securities, less than 12 months	669,839	2,386,847
Fair value of unrealized losses on available for sale securities, 12 months or more	1,719,118	467,340
Total fair value of unrealized losses on available for sale securities	2,388,957	2,854,187
US Treasury Securities [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	(1)
Unrealized losses on available for sale securities, 12 months or more	0
Total unrealized losses on available for sale securities	(1)
Fair value of unrealized losses on available for sale securities, less than 12 months	998
Fair value of unrealized losses on available for sale securities, 12 months or more	0
Total fair value of unrealized losses on available for sale securities	998
Number of available for sale securities in a continuous unrealized loss position less than twelve months	1
Number of available for sale securities in a continuous unrealized loss position for twelve months or more
Obligations of state and political subdivisions (municipal securities) [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	(9)	(1,525)
Unrealized losses on available for sale securities, 12 months or more	(20)	(8)
Total unrealized losses on available for sale securities	(29)	(1,533)
Fair value of unrealized losses on available for sale securities, less than 12 months	3,374	47,044
Fair value of unrealized losses on available for sale securities, 12 months or more	2,133	273
Total fair value of unrealized losses on available for sale securities	5,507	47,317
Number of available for sale securities in a continuous unrealized loss position less than twelve months	6	113
Number of available for sale securities in a continuous unrealized loss position for twelve months or more	6	1
Government-Sponsored Enterprise (GSE) [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	(1,404)	(57,393)
Unrealized losses on available for sale securities, 12 months or more	(29,146)	(21,186)
Total unrealized losses on available for sale securities	(30,550)	(78,579)
Fair value of unrealized losses on available for sale securities, less than 12 months	333,713	1,887,784
Fair value of unrealized losses on available for sale securities, 12 months or more	1,256,533	421,082
Total fair value of unrealized losses on available for sale securities	1,590,246	2,308,866
Number of available for sale securities in a continuous unrealized loss position less than twelve months	16	106
Number of available for sale securities in a continuous unrealized loss position for twelve months or more	56	15
Private Label [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	(9)	(37)
Unrealized losses on available for sale securities, 12 months or more	(1)	0
Total unrealized losses on available for sale securities	(10)	(37)
Fair value of unrealized losses on available for sale securities, less than 12 months	1,772	2,105
Fair value of unrealized losses on available for sale securities, 12 months or more	27	35
Total fair value of unrealized losses on available for sale securities	1,799	2,140
Number of available for sale securities in a continuous unrealized loss position less than twelve months	1	2
Number of available for sale securities in a continuous unrealized loss position for twelve months or more	2	1
GSE Commercial Mortgage-Related Securities [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	(1,766)	(23,854)
Unrealized losses on available for sale securities, 12 months or more	(24,176)	(3,988)
Total unrealized losses on available for sale securities	(25,942)	(27,842)
Fair value of unrealized losses on available for sale securities, less than 12 months	329,982	443,462
Fair value of unrealized losses on available for sale securities, 12 months or more	460,425	45,950
Total fair value of unrealized losses on available for sale securities	790,407	489,412
Number of available for sale securities in a continuous unrealized loss position less than twelve months	9	19
Number of available for sale securities in a continuous unrealized loss position for twelve months or more	20	1
Asset-backed Securities [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months		0
Unrealized losses on available for sale securities, 12 months or more		0
Total unrealized losses on available for sale securities		0
Fair value of unrealized losses on available for sale securities, less than 12 months		0
Fair value of unrealized losses on available for sale securities, 12 months or more		0
Total fair value of unrealized losses on available for sale securities		0
Number of available for sale securities in a continuous unrealized loss position less than twelve months		0
Number of available for sale securities in a continuous unrealized loss position for twelve months or more		0
Other Debt And Other Equity Securities [Member]
Unrealized losses and fair value of available for sale securities , by investment category and time length
Unrealized losses on available for sale securities, less than 12 months	0	(43)
Unrealized losses on available for sale securities, 12 months or more	0	0
Total unrealized losses on available for sale securities	0	(43)
Fair value of unrealized losses on available for sale securities, less than 12 months	0	6,452
Fair value of unrealized losses on available for sale securities, 12 months or more	0	0
Total fair value of unrealized losses on available for sale securities	$ 0	$ 6,452
Number of available for sale securities in a continuous unrealized loss position less than twelve months	0	5
Number of available for sale securities in a continuous unrealized loss position for twelve months or more	0	0