Investment Securities (Credit Losses on Impaired Securities) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
OTTI credit losses on previously impaired securities	$ 0	$ 0
Securities Available for Sale
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Beginning balance	1,892	1,863
OTTI credit losses on previously impaired securities	0	0
Ending balance	$ 1,892	$ 1,863