Fair Value Measurements (Narrative) (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013 Impaired_Loans	Dec. 31, 2012 Impaired_Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	$ 2,525,041,000	$ 2,399,488,000
Number of impaired loans	14	7
Allowance related to impaired loans	10,868,000	7,120,000
Impaired loans, charge-offs		2,600,000
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
Inventory and Equipment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans, collateral, discount rate	50.00%
Accounts Receivable [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans, collateral, discount rate	20.00%
Foreclosed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans, collateral, discount rate	15.00%
Minimum [Member] | Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans, collateral, discount rate	15.00%
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, maximum original maturities	90 days	90 days
Maximum [Member] | Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans, collateral, discount rate	35.00%
Weighted average [Member] | Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans, collateral, discount rate	22.00%
Fair value measurements, recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities	0	0
Fair value measurements, nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with specific allocation	13,776,000	11,991,000
Impaired loans net of partial charge-offs	3,842,000	4,227,000
Foreclosed assets, carrying value	0	0
Fair value inputs, Level 3 [Member] | Fair value measurements, nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with specific allocation	13,776,000	11,991,000
Allowance related to impaired loans	10,900,000	7,100,000
Impaired loans net of partial charge-offs	3,842,000	4,227,000
Impaired loans, charge-offs	$ 2,700,000