Fair Value Measurements (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Assets:
Investment securities, available-for-sale	$ 839,597	$ 832,700
Trading account securities	192	192
Mortgages held for sale	10,961	6,079
Liabilities:
Accrued expenses and other liabilities	134,592	128,324
U.S. Treasury and Federal agencies securities
Assets:
Investment securities, available-for-sale	401,390	395,039
U.S. States and political subdivisions securities
Assets:
Investment securities, available-for-sale	127,394	123,239
Mortgage-backed securities - Federal agencies
Assets:
Investment securities, available-for-sale	269,520	275,080
Corporate debt securities
Assets:
Investment securities, available-for-sale	32,140	31,065
Foreign government and other securities
Assets:
Investment securities, available-for-sale	702	709
Total debt securities
Assets:
Investment securities, available-for-sale	831,146	825,132
Marketable equity securities
Assets:
Investment securities, available-for-sale	8,451	7,568
Recurring basis | Level 1
Assets:
Investment securities, available-for-sale	28,132	27,199
Trading account securities	192	192
Mortgages held for sale	0	0
Total	28,324	27,391
Liabilities:
Total	0	0
Recurring basis | Level 1 | Interest rate swap contracts
Assets:
Accrued income and other assets	0	0
Liabilities:
Accrued expenses and other liabilities	0	0
Recurring basis | Level 1 | U.S. Treasury and Federal agencies securities
Assets:
Investment securities, available-for-sale	19,681	19,631
Recurring basis | Level 1 | U.S. States and political subdivisions securities
Assets:
Investment securities, available-for-sale	0	0
Recurring basis | Level 1 | Mortgage-backed securities - Federal agencies
Assets:
Investment securities, available-for-sale	0	0
Recurring basis | Level 1 | Corporate debt securities
Assets:
Investment securities, available-for-sale	0	0
Recurring basis | Level 1 | Foreign government and other securities
Assets:
Investment securities, available-for-sale	0	0
Recurring basis | Level 1 | Total debt securities
Assets:
Investment securities, available-for-sale	19,681	19,631
Recurring basis | Level 1 | Marketable equity securities
Assets:
Investment securities, available-for-sale	8,451	7,568
Recurring basis | Level 2
Assets:
Investment securities, available-for-sale	806,756	800,003
Trading account securities	0	0
Mortgages held for sale	10,961	6,079
Total	827,248	815,976
Liabilities:
Total	9,719	10,087
Recurring basis | Level 2 | Interest rate swap contracts
Assets:
Accrued income and other assets	9,531	9,894
Liabilities:
Accrued expenses and other liabilities	9,719	10,087
Recurring basis | Level 2 | U.S. Treasury and Federal agencies securities
Assets:
Investment securities, available-for-sale	381,709	375,408
Recurring basis | Level 2 | U.S. States and political subdivisions securities
Assets:
Investment securities, available-for-sale	122,685	117,741
Recurring basis | Level 2 | Mortgage-backed securities - Federal agencies
Assets:
Investment securities, available-for-sale	269,520	275,080
Recurring basis | Level 2 | Corporate debt securities
Assets:
Investment securities, available-for-sale	32,140	31,065
Recurring basis | Level 2 | Foreign government and other securities
Assets:
Investment securities, available-for-sale	702	709
Recurring basis | Level 2 | Total debt securities
Assets:
Investment securities, available-for-sale	806,756	800,003
Recurring basis | Level 2 | Marketable equity securities
Assets:
Investment securities, available-for-sale	0	0
Recurring basis | Level 3
Assets:
Investment securities, available-for-sale	4,709	5,498
Trading account securities	0	0
Mortgages held for sale	0	0
Total	4,709	5,498
Liabilities:
Total	0	0
Recurring basis | Level 3 | Interest rate swap contracts
Assets:
Accrued income and other assets	0	0
Liabilities:
Accrued expenses and other liabilities	0	0
Recurring basis | Level 3 | U.S. Treasury and Federal agencies securities
Assets:
Investment securities, available-for-sale	0	0
Recurring basis | Level 3 | U.S. States and political subdivisions securities
Assets:
Investment securities, available-for-sale	4,709	5,498
Recurring basis | Level 3 | Mortgage-backed securities - Federal agencies
Assets:
Investment securities, available-for-sale	0	0
Recurring basis | Level 3 | Corporate debt securities
Assets:
Investment securities, available-for-sale	0	0
Recurring basis | Level 3 | Foreign government and other securities
Assets:
Investment securities, available-for-sale	0	0
Recurring basis | Level 3 | Total debt securities
Assets:
Investment securities, available-for-sale	4,709	5,498
Recurring basis | Level 3 | Marketable equity securities
Assets:
Investment securities, available-for-sale	0	0
Recurring basis | Total
Assets:
Investment securities, available-for-sale	839,597	832,700
Trading account securities	192	192
Mortgages held for sale	10,961	6,079
Total	860,281	848,865
Liabilities:
Total	9,719	10,087
Recurring basis | Total | Interest rate swap contracts
Assets:
Accrued income and other assets	9,531	9,894
Liabilities:
Accrued expenses and other liabilities	9,719	10,087
Recurring basis | Total | U.S. Treasury and Federal agencies securities
Assets:
Investment securities, available-for-sale	401,390	395,039
Recurring basis | Total | U.S. States and political subdivisions securities
Assets:
Investment securities, available-for-sale	127,394	123,239
Recurring basis | Total | Mortgage-backed securities - Federal agencies
Assets:
Investment securities, available-for-sale	269,520	275,080
Recurring basis | Total | Corporate debt securities
Assets:
Investment securities, available-for-sale	32,140	31,065
Recurring basis | Total | Foreign government and other securities
Assets:
Investment securities, available-for-sale	702	709
Recurring basis | Total | Total debt securities
Assets:
Investment securities, available-for-sale	831,146	825,132
Recurring basis | Total | Marketable equity securities
Assets:
Investment securities, available-for-sale	$ 8,451	$ 7,568