Securities Available For Sale Securtities Available For Sale (Other Than Temporary Losses Recognized on Auction Rate Securities) (Details) (USD $)	12 Months Ended			27 Months Ended	39 Months Ended	12 Months Ended			39 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Auction Rate Securities [Member]	Dec. 31, 2012 Auction Rate Securities [Member]	Dec. 31, 2012 Collateralized Debt Obligations [Member] Auction Rate Securities [Member]	Dec. 31, 2011 Collateralized Debt Obligations [Member] Auction Rate Securities [Member]	Dec. 31, 2010 Collateralized Debt Obligations [Member] Auction Rate Securities [Member]	Dec. 31, 2012 Collateralized Debt Obligations [Member] Auction Rate Securities [Member]
Gain (Loss) on Investments [Line Items]
Total other-than-temporary impairment losses on securities available for sale							$ 600,000	$ 1,200,000
Less: unrealized losses on securities available for sale, recognized in other comprehensive income							0	0
Cumulative credit and other losses recognized in earnings	$ 0	$ 574,000	$ 1,164,000	$ 3,300,000	$ 3,300,000	$ 0	$ 600,000	$ 1,200,000	$ 3,300,000