Fair Values of Assets and Liabilities (Details 5) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011
Financial assets
Cash and due from banks	$ 82,659	$ 74,967
Interest-bearing bank deposits	3,839	3,511
Securities available for sale	1,159,202	1,142,776
Other investments	35,916	39,796
Loans held for sale	0	13,412
Loans	4,159,531	4,043,643	3,992,058
Financial liabilities
Deposits	4,461,962	4,504,684
Short-term borrowings	474,264	312,777
Long-term debt	75,370	101,664
Subordinated debt	105,750	105,750
Fair Value, Inputs, Level 1 [Member]
Financial assets
Other investments	0	0
Fair Value, Inputs, Level 2 [Member]
Financial assets
Other investments	35,916	39,796
Fair Value, Inputs, Level 3 [Member]
Financial assets
Other investments	0	0
Carrying Value [Member]
Financial assets
Cash and due from banks	82,659	74,967
Interest-bearing bank deposits	3,839	3,511
Securities available for sale	1,159,202	1,142,776
Other investments	35,916	39,796
Loans held for sale		13,412
Loans	4,159,531	4,043,643
Financial liabilities
Deposits	4,461,962	4,504,684
Short-term borrowings	474,264	312,777
Long-term debt	75,370	101,664
Subordinated debt	105,750	105,750
Estimated Fair Value [Member]
Financial assets
Cash and due from banks	82,659	74,967
Interest-bearing bank deposits	3,839	3,511
Securities available for sale	1,159,202	1,142,776
Other investments	35,916	39,796
Loans held for sale		13,412
Loans	4,220,966	4,113,525
Financial liabilities
Deposits	4,405,479	4,452,235
Short-term borrowings	474,255	312,777
Long-term debt	78,068	103,749
Subordinated debt	74,646	75,310
Estimated Fair Value [Member] | Fair Value, Inputs, Level 1 [Member]
Financial assets
Cash and due from banks	82,659
Interest-bearing bank deposits	3,839
Securities available for sale	440
Other investments	0
Loans	0
Financial liabilities
Deposits	0
Short-term borrowings	0
Long-term debt	0
Subordinated debt	0
Estimated Fair Value [Member] | Fair Value, Inputs, Level 2 [Member]
Financial assets
Cash and due from banks	0
Interest-bearing bank deposits	0
Securities available for sale	1,135,550
Other investments	35,916
Loans	50,473
Financial liabilities
Deposits	4,405,479
Short-term borrowings	474,255
Long-term debt	78,068
Subordinated debt	0
Estimated Fair Value [Member] | Fair Value, Inputs, Level 3 [Member]
Financial assets
Cash and due from banks	0
Interest-bearing bank deposits	0
Securities available for sale	23,212
Other investments	0
Loans	4,170,493
Financial liabilities
Deposits	0
Short-term borrowings	0
Long-term debt	0
Subordinated debt	$ 74,646