Securities Sold Under Agreements to Repurchase and Other Short-Term Debt (Information Regarding Other Borrowed Funds) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Short-term Debt [Line Items]
Amount outstanding at year end	$ 287,520	$ 262,527
FHLB Short Term Borrowings [Member]
Short-term Debt [Line Items]
Amount outstanding at year end	0	0	0
Average amount outstanding	38,290	359	1,316
Weighted average-rate during the year	0.28%	0.28%	0.31%
Weighted average rate at year-end	0.00%	0.00%	0.00%
Maximum amount outstanding during the year	97,000	0	13,000
Demand Note Due U.S. Treasury [Member]
Short-term Debt [Line Items]
Amount outstanding at year end	0	0	2,964
Maximum amount outstanding during the year	0	3,013	3,330
Average amount outstanding	0	1,794	1,414
Weighted average-rate during the year	0.00%	0.00%	0.00%
Weighted average rate at year-end	0.00%	0.00%	0.00%
Securities Sold under Agreement to Repurchase - Short-Term [Member]
Short-term Debt [Line Items]
Amount outstanding at year end	287,520	262,527	224,693
Maximum amount outstanding during the year	303,420	266,897	224,693
Average amount outstanding	$ 230,281	$ 217,823	$ 172,165
Weighted average-rate during the year	0.73%	0.95%	0.94%
Weighted average rate at year-end	0.47%	0.91%	1.01%