Investment Securities Noncredit Related Other Than Temporary Impairment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Noncredit Related Losses On Securities Not Expected To Be Sold [Line Items]
Noncredit-related losses on securities not expected to be sold (recognized in other comprehensive income)	$ 1,140	$ 42,196	$ 25,922	$ 43,377
Held-to-maturity Securities [Member]
Noncredit Related Losses On Securities Not Expected To Be Sold [Line Items]
Noncredit-related losses on securities not expected to be sold (recognized in other comprehensive income)	0	20,945	16,718	20,945
Available-for-sale Securities [Member]
Noncredit Related Losses On Securities Not Expected To Be Sold [Line Items]
Noncredit-related losses on securities not expected to be sold (recognized in other comprehensive income)	$ 1,140	$ 21,251	$ 9,204	$ 22,432