Fair Value Accounting and Measurement (Carrying Amounts and Estimated Fair Values of Selected Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Assets
Interest-earning deposits with banks	$ 356,056	$ 389,353
Securities available for sale	1,012,162	1,001,665
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Assets
Cash and due from banks	91,889	124,573
Interest-earning deposits with banks	356,056	389,353
Securities available for sale	1,012,162	1,001,665
FHLB stock	21,621	21,819
Loans held for sale	888	2,563
Loans	2,933,306	2,864,803
FDIC loss-sharing asset	83,115	96,354
Interest rate contracts	13,456	14,921
Liabilities
Deposits	4,046,539	4,042,085
FHLB Advances	6,634	6,644
Repurchase agreements	25,000	25,000
Interest rate contracts	13,456	14,921
Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	91,889	124,573
Interest-earning deposits with banks	356,056	389,353
Securities available for sale	1,012,162	1,001,665
FHLB stock	21,621	21,819
Loans held for sale	888	2,563
Loans	2,978,867	2,944,317
FDIC loss-sharing asset	25,062	26,543
Interest rate contracts	13,456	14,921
Liabilities
Deposits	4,047,346	4,043,221
FHLB Advances	6,237	5,894
Repurchase agreements	26,396	26,464
Interest rate contracts	13,456	14,921
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	91,889	124,573
Interest-earning deposits with banks	356,056	389,353
Securities available for sale	19,706	19,828
FHLB stock	0	0
Loans held for sale	0	0
Loans	0	0
FDIC loss-sharing asset	0	0
Interest rate contracts	0	0
Liabilities
Deposits	3,573,755	3,549,821
FHLB Advances	0	0
Repurchase agreements	0	0
Interest rate contracts	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	0	0
Interest-earning deposits with banks	0	0
Securities available for sale	992,456	981,837
FHLB stock	21,621	21,819
Loans held for sale	888	2,563
Loans	0	0
FDIC loss-sharing asset	0	0
Interest rate contracts	13,456	14,921
Liabilities
Deposits	473,591	493,400
FHLB Advances	6,237	5,894
Repurchase agreements	26,396	26,464
Interest rate contracts	13,456	14,921
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and due from banks	0	0
Interest-earning deposits with banks	0	0
Securities available for sale	0	0
FHLB stock	0	0
Loans held for sale	0	0
Loans	2,978,867	2,944,317
FDIC loss-sharing asset	25,062	26,543
Interest rate contracts	0	0
Liabilities
Deposits	0	0
FHLB Advances	0	0
Repurchase agreements	0	0
Interest rate contracts	$ 0	$ 0