Securities (Schedule of Cumulative Credit-Related OTTI Charges Recognized as Components of Earnings for Securities for which a portion of an OTTI is Recognized in Other Comprehensive Income) (Details) (USD $) In Thousands	12 Months Ended
	Dec. 31, 2010	Jun. 30, 2011
Securities
Beginning balance of the amount related to credit loss for which a portion of OTTI was recognized in other comprehensive income	$ (16,051)	$ (18,332)
Additions related to credit loss for securities with previously recognized OTTI	(2,235)
Additions related to credit loss for securities with initial OTTI	(46)
Ending balance of the amount related to credit loss for which a portion of OTTI was recognized in other comprehensive income	$ (18,332)	$ (18,332)