Investment Securities Noncredit Related Other Than Temporary Impairment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 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)	$ 16,718	$ 1,181	$ 24,782	$ 1,181
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)	16,718	0	16,718	0
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)	$ 0	$ 1,181	$ 8,064	$ 1,181