Securities Purchased Under Agreements To Resell (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Securities Purchased Under Agreements To Resell [Abstract]
Resale agreements		$ 110,000,000
Resale agreements, Percentage		0.20%
Resale agreements, maturities		March 9, 2011
Balance, December 31		110,000,000
Annualized weighted-average interest rate, December 31	0.00%	0.20%
Daily average amount outstanding during the year	84,493,000	6,932,000
Weighted-average interest rate for the year	0.10%	0.20%
Maximum amount outstanding at any month end	255,000,000	110,000,000
Interest income associated with securities purchased under resale agreements	$ 83,000	$ 14,000	$ 1,300,000