Investment Securities Noncredit Related Other Than Temporary Impairment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
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)	$ 693	$ 16,718	$ 22,069	$ 24,782
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	16,718	16,114	16,718
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)	$ 693	$ 0	$ 5,955	$ 8,064