Securities in an Unrealized Loss Position (Roll-Forward of Portion of Impairments) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Securities In An Unrealized Loss Position [Abstract]
Beginning balance of amounts related to credit losses	$ 4,261	$ 5,661
Additions for amounts related to credit losses	0	0
Deductions for amounts related to credit loss sales	0	(1,400)
Ending balance of amounts related to credit losses	$ 4,261	$ 4,261