Securities in an Unrealized Loss Position (Roll-Forward of Portion of Impairments) (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Securities In An Unrealized Loss Position
Beginning balance of amounts related to credit losses	$ 4,261	$ 5,661	$ 4,261	$ 5,661
Additions for amounts related to credit losses
Ending balance of amounts related to credit losses	$ 4,261	$ 5,661	$ 4,261	$ 5,661