Securities Credit Impaired Debt Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Changes in the credit loss component of credit-impaired debt securities
Other Than Temporary Impairment Credit Losses Recognized In Earnings Credit Losses On Debt Securities Held	$ 1,257	$ 3,276
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, Additional Credit Losses	0	130
Other Than Temporary Impairment Credit Losses Recognized In Earnings, Reductions, Securities Sold	0	2,149
Other Than Temporary Impairment Credit Losses Recognized In Earnings Credit Losses On Debt Securities Held	$ 1,257	$ 1,257