Investment Securities AFS unreal losses and FV of unreal losses (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
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	$ (4,832)	$ (2,133)
Unrealized losses on available for sale securities, 12 months or more	(88)	(1,530)
Total unrealized losses on available for sale securities	(4,920)	(3,663)
Fair value of unrealized losses on available for sale securities, less than 12 months	1,000,503	237,411
Fair value of unrealized losses on available for sale securities, 12 months or more	459	176,979
Total fair value of unrealized losses on available for sale securities	1,000,962	414,390
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	(42)	(10)
Unrealized losses on available for sale securities, 12 months or more	(13)	(18)
Total unrealized losses on available for sale securities	(55)	(28)
Fair value of unrealized losses on available for sale securities, less than 12 months	5,065	971
Fair value of unrealized losses on available for sale securities, 12 months or more	348	348
Total fair value of unrealized losses on available for sale securities	5,413	1,319
Number of available for sale securities in a continuous unrealized loss position less than twelve months	15
Number of available for sale securities in a continuous unrealized loss position for twelve months or more	1
Residential 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	(3,727)	(1,443)
Unrealized losses on available for sale securities, 12 months or more	0	(20)
Total unrealized losses on available for sale securities	(3,727)	(1,463)
Fair value of unrealized losses on available for sale securities, less than 12 months	892,964	186,954
Fair value of unrealized losses on available for sale securities, 12 months or more	0	1,469
Total fair value of unrealized losses on available for sale securities	892,964	188,423
Number of available for sale securities in a continuous unrealized loss position less than twelve months	30
Number of available for sale securities in a continuous unrealized loss position for twelve months or more	0
Commercial Mortgage 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	(1,063)
Unrealized losses on available for sale securities, 12 months or more	0
Total unrealized losses on available for sale securities	(1,063)
Fair value of unrealized losses on available for sale securities, less than 12 months	102,474
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	102,474
Number of available for sale securities in a continuous unrealized loss position less than twelve months	2
Number of available for sale securities in a continuous unrealized loss position for twelve months or more	0
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		(9)
Unrealized losses on available for sale securities, 12 months or more		(698)
Total unrealized losses on available for sale securities		(707)
Fair value of unrealized losses on available for sale securities, less than 12 months		4,091
Fair value of unrealized losses on available for sale securities, 12 months or more		174,640
Total fair value of unrealized losses on available for sale securities		178,731
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	(671)
Unrealized losses on available for sale securities, 12 months or more	(75)	(794)
Total unrealized losses on available for sale securities	(75)	(1,465)
Fair value of unrealized losses on available for sale securities, less than 12 months	0	45,395
Fair value of unrealized losses on available for sale securities, 12 months or more	111	522
Total fair value of unrealized losses on available for sale securities	$ 111	$ 45,917
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	1

Number of available for sale securities in a continuous unrealized loss position less than twelve months

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Number of available for sale securities in a continuous unrealized loss position twelve months or longer aggregate losses.

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Amount of the excess of amortized cost basis over fair value of securities that have been in a loss position for twelve months or longer for securities which are categorized neither as held-to-maturity nor trading securities.

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This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

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