Fair Values of Financial Instruments (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Financial assets [Abstract]
Securities available for sale, at fair value	$ 1,244,619,000	$ 1,129,368,000
Securities held to maturity	70,811,000	97,310,000
Trading securities	3,062,000	2,808,000
Net loans and leases	3,728,869,000	3,538,772,000
Financial liabilities [Abstract]
Savings, NOW, and money market	2,381,116,000	2,291,833,000
Time deposits	933,127,000	930,778,000
Noninterest bearing	1,052,906,000	911,741,000
Short-term borrowings	181,592,000	159,434,000
Long-term debt	370,344,000	369,874,000
Trust preferred debentures	75,422,000	75,422,000
Securities Available for Sale: [Abstract]
Securities Available for Sale	1,244,619,000	1,129,368,000
Trading Securities	3,062,000	2,808,000
Collateral dependent impaired loans with no specific reserve	500,000
Reserves on collateral dependent impaired loans	200,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Financial assets [Abstract]
Securities available for sale, at fair value	91,058,000	99,470,000
Trading securities	3,062,000	2,808,000
Securities Available for Sale: [Abstract]
U.S. Treasury	82,233,000	91,280,000
Federal Agency	0	0
State & municipal	0	0
Mortgage-backed	0	0
Collateralized mortgage obligations	0	0
Corporate	0	0
Other securities	8,825,000	8,190,000
Securities Available for Sale	91,058,000	99,470,000
Trading Securities	3,062,000	2,808,000
Total	94,120,000	102,278,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Financial assets [Abstract]
Securities available for sale, at fair value	1,153,561,000	1,029,898,000
Trading securities	0	0
Securities Available for Sale: [Abstract]
U.S. Treasury	0	0
Federal Agency	255,846,000	349,750,000
State & municipal	104,789,000	114,937,000
Mortgage-backed	325,397,000	244,808,000
Collateralized mortgage obligations	465,475,000	297,888,000
Corporate	0	20,489,000
Other securities	2,054,000	2,026,000
Securities Available for Sale	1,153,561,000	1,029,898,000
Trading Securities	0	0
Total	1,153,561,000	1,029,898,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Financial assets [Abstract]
Securities available for sale, at fair value	0	0
Trading securities	0	0
Securities Available for Sale: [Abstract]
U.S. Treasury	0	0
Federal Agency	0	0
State & municipal	0	0
Mortgage-backed	0	0
Collateralized mortgage obligations	0	0
Corporate	0	0
Other securities	0	0
Securities Available for Sale	0	0
Trading Securities	0	0
Total	0	0
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Financial assets [Abstract]
Securities available for sale, at fair value	1,244,619,000	1,129,368,000
Trading securities	3,062,000	2,808,000
Securities Available for Sale: [Abstract]
U.S. Treasury	82,233,000	91,280,000
Federal Agency	255,846,000	349,750,000
State & municipal	104,789,000	114,937,000
Mortgage-backed	325,397,000	244,808,000
Collateralized mortgage obligations	465,475,000	297,888,000
Corporate	0	20,489,000
Other securities	10,879,000	10,216,000
Securities Available for Sale	1,244,619,000	1,129,368,000
Trading Securities	3,062,000	2,808,000
Total	1,247,681,000	1,132,176,000
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Financial assets [Abstract]
Cash and cash equivalents	129,381,000	168,792,000
Securities available for sale, at fair value	1,244,619,000	1,129,368,000
Securities held to maturity	70,811,000	97,310,000
Trading securities	3,062,000	2,808,000
Net loans and leases	3,728,869,000	3,538,772,000
Accrued interest receivable	17,800,000	19,130,000
Financial liabilities [Abstract]
Savings, NOW, and money market	2,381,116,000	2,291,833,000
Time deposits	933,127,000	930,778,000
Noninterest bearing	1,052,906,000	911,741,000
Short-term borrowings	181,592,000	159,434,000
Long-term debt	370,344,000	369,874,000
Accrued interest payable	3,942,000	4,356,000
Trust preferred debentures	75,422,000	75,422,000
Securities Available for Sale: [Abstract]
Securities Available for Sale	1,244,619,000	1,129,368,000
Trading Securities	3,062,000	2,808,000
Estimate of Fair Value, Fair Value Disclosure [Member]
Financial assets [Abstract]
Cash and cash equivalents	129,381,000	168,792,000
Securities available for sale, at fair value	1,244,619,000	1,129,368,000
Securities held to maturity	72,198,000	98,759,000
Trading securities	3,062,000	2,808,000
Net loans and leases	3,821,640,000	3,626,603,000
Accrued interest receivable	17,800,000	19,130,000
Financial liabilities [Abstract]
Savings, NOW, and money market	2,381,116,000	2,291,833,000
Time deposits	942,436,000	943,988,000
Noninterest bearing	1,052,906,000	911,741,000
Short-term borrowings	181,592,000	159,434,000
Long-term debt	427,107,000	423,350,000
Accrued interest payable	3,942,000	4,356,000
Trust preferred debentures	75,422,000	71,148,000
Securities Available for Sale: [Abstract]
Securities Available for Sale	1,244,619,000	1,129,368,000
Trading Securities	$ 3,062,000	$ 2,808,000