Fair Value Measurement (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Financial assets:
Cash and due from banks	$ 178,263	$ 125,605	$ 157,243	$ 140,325
Total securities - available-for-sale	993,270	1,021,244
Held-to-maturity, Amortized cost	592,033	602,509
Net loans	3,632,137	3,635,063
Loans held for sale	14,299	21,903
Accrued interest receivable	19,909	19,354
Bank-owned life insurance	118,666	119,671
Financial Liabilities
Deposits	5,006,202	4,944,284
Federal Home Loan Bank borrowings	60,767	111,187
Other borrowings	128,372	142,971
Junior subordinated debt	106,109	113,832
Accrued interest payable	3,620	3,856
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets:
Cash and due from banks	178,263	125,605
Total securities - available-for-sale	8,986	9,059
Accrued interest receivable	19,909	19,354
Bank-owned life insurance	118,666	119,671
Financial Liabilities
Deposits	3,373,842	3,294,664
Other borrowings	81,286	95,768
Accrued interest payable	3,620	3,856
Significant Other Observable Inputs (Level 2) [Member]
Financial assets:
Total securities - available-for-sale	984,284	1,012,162
Held-to-maturity, Amortized cost	623,824	638,469
Loans held for sale	14,299	21,903
Financial Liabilities
Deposits	1,657,827	1,668,692
Federal Home Loan Bank borrowings	66,083	114,461
Other borrowings	50,932	46,985
Junior subordinated debt	63,610	64,624
Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Total securities - available-for-sale		23
Held-to-maturity, Amortized cost	803	804
Net loans	3,622,794	3,600,068
Carrying Amount [Member]
Financial assets:
Cash and due from banks	178,263	125,605
Total securities - available-for-sale	993,270	1,021,244
Held-to-maturity, Amortized cost	592,033	602,509
Net loans	3,632,137	3,635,063
Loans held for sale	14,299	21,903
Accrued interest receivable	19,909	19,354
Bank-owned life insurance	118,666	119,671
Financial Liabilities
Deposits	5,006,202	4,944,284
Federal Home Loan Bank borrowings	60,767	111,187
Other borrowings	128,372	142,971
Junior subordinated debt	106,109	113,832
Accrued interest payable	3,620	3,856
Fair Value Estimate [Member]
Financial assets:
Cash and due from banks	178,263	125,605
Total securities - available-for-sale	993,270	1,021,244
Held-to-maturity, Amortized cost	624,627	639,273
Net loans	3,622,794	3,600,068
Loans held for sale	14,299	21,903
Accrued interest receivable	19,909	19,354
Bank-owned life insurance	118,666	119,671
Financial Liabilities
Deposits	5,031,669	4,963,356
Federal Home Loan Bank borrowings	66,083	114,461
Other borrowings	132,218	142,753
Junior subordinated debt	63,610	64,624
Accrued interest payable	$ 3,620	$ 3,856