Investment Securities (Credit Losses on Impaired Securities) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
OTTI credit losses on previously impaired securities	$ 29	$ 631	$ 403
Securities Available for Sale
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	1,863	1,232	829
OTTI credit losses on previously impaired securities	29	631	403
Ending balance	$ 1,892	$ 1,863	$ 1,232