Fair Value Measurements (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Financial assets:
Cash and due from banks	$ 102,815	$ 140,325	$ 83,345	$ 79,136
Available-for-sale, at fair value	1,023,124	1,016,340
Held-to-maturity (fair values of $607,032 and $621,472, respectively)	572,671	592,925
Net loans	3,222,220	3,184,558
Loans held for sale	7,305	6,084
Accrued interest receivable	18,233	19,268
Bank-owned life insurance	111,829	110,074
Financial liabilities:
Deposits	4,393,782	4,393,866
Federal Home Loan Bank borrowings	141,877	168,186
Other borrowings	191,275	196,887
Junior subordinated debt	106,083	106,066
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets:
Cash and due from banks	102,815
Available-for-sale, at fair value	3,877
Held-to-maturity (fair values of $607,032 and $621,472, respectively)
Net loans
Loans held for sale
Accrued interest receivable	18,233
Bank-owned life insurance	111,829
Financial liabilities:
Deposits	2,888,650
Federal Home Loan Bank borrowings
Other borrowings	93,116
Junior subordinated debt
Accrued interest payable	4,741
Significant Other Observable Inputs (Level 2) [Member]
Financial assets:
Cash and due from banks
Available-for-sale, at fair value	1,019,223
Held-to-maturity (fair values of $607,032 and $621,472, respectively)	606,236
Net loans
Loans held for sale	7,305
Accrued interest receivable
Bank-owned life insurance
Financial liabilities:
Deposits	1,532,283
Federal Home Loan Bank borrowings	146,648
Other borrowings	98,586
Junior subordinated debt	56,083
Accrued interest payable
Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Cash and due from banks
Available-for-sale, at fair value	24
Held-to-maturity (fair values of $607,032 and $621,472, respectively)	796
Net loans	3,168,829
Loans held for sale
Accrued interest receivable
Bank-owned life insurance
Financial liabilities:
Deposits
Federal Home Loan Bank borrowings
Other borrowings
Junior subordinated debt
Accrued interest payable
Carrying Amount [Member]
Financial assets:
Cash and due from banks	102,815	140,325
Available-for-sale, at fair value	1,023,124	1,016,340
Held-to-maturity (fair values of $607,032 and $621,472, respectively)	572,671	592,925
Net loans	3,222,220	3,184,558
Loans held for sale	7,305	6,084
Accrued interest receivable	18,233	19,268
Bank-owned life insurance	111,829	110,074
Financial liabilities:
Deposits	4,393,782	4,393,866
Federal Home Loan Bank borrowings	141,877	168,186
Other borrowings	191,275	196,887
Junior subordinated debt	106,083	106,066
Accrued interest payable	4,741	4,975
Fair Value [Member]
Financial assets:
Cash and due from banks	102,815	140,325
Available-for-sale, at fair value	1,023,124	1,016,340
Held-to-maturity (fair values of $607,032 and $621,472, respectively)	607,032	621,472
Net loans	3,168,829	3,068,799
Loans held for sale	7,305	6,084
Accrued interest receivable	18,233	19,268
Bank-owned life insurance	111,829	110,074
Financial liabilities:
Deposits	4,420,933	4,420,102
Federal Home Loan Bank borrowings	146,648	174,926
Other borrowings	191,702	197,922
Junior subordinated debt	56,083	56,515
Accrued interest payable	$ 4,741	$ 4,975