Fair Value Measurements (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended	6 Months Ended					12 Months Ended	6 Months Ended
	Jun. 30, 2013 Impaired_Loans	Dec. 31, 2012 Impaired_Loans	Jun. 30, 2013 Inventory and Equipment [Member]	Jun. 30, 2013 Accounts Receivable [Member]	Jun. 30, 2013 Foreclosed [Member]	Jun. 30, 2013 Minimum [Member] Real Estate [Member]	Jun. 30, 2013 Maximum [Member]	Dec. 31, 2012 Maximum [Member]	Jun. 30, 2013 Maximum [Member] Real Estate [Member]	Jun. 30, 2013 Fair value measurements, recurring [Member]	Dec. 31, 2012 Fair value measurements, recurring [Member]	Jun. 30, 2013 Fair value measurements, nonrecurring [Member]	Dec. 31, 2012 Fair value measurements, nonrecurring [Member]	Jun. 30, 2013 Fair value inputs, Level 3 [Member] Fair value measurements, nonrecurring [Member]	Dec. 31, 2012 Fair value inputs, Level 3 [Member] Fair value measurements, nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	$ 2,429,937,000	$ 2,399,488,000								$ 0	$ 0
Impaired loans, collateral, discount rate			50.00%	20.00%	15.00%	15.00%			35.00%
Number of impaired loans	10	7
Impaired loans with specific allocation												11,996,000	11,991,000	11,996,000	11,991,000
Allowance related to impaired loans	10,335,000	7,120,000												10,300,000	7,100,000
Impaired loans net of partial charge-offs												2,142,000	4,227,000	2,142,000	4,227,000
Impaired loans, charge-offs		2,600,000												1,300,000
Foreclosed assets, carrying value												0	0
Cash and cash equivalents, maximum original maturities							90 days	90 days
Fair value measurements, transfers between levels 1 and 2	0
Fair value measurements, transfers between levels 2 and 3	0
Loans Held-for-sale, Write Down	$ 0	$ 0