Fair Value Measurements (Details 2) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets:
Investment securities, available-for-sale	$ 893,973	$ 850,467
Mortgages held for sale	11,000	15,849
U.S. Treasury and Federal agencies securities
Assets:
Investment securities, available-for-sale	457,626	420,833
U.S. States and political subdivisions securities
Assets:
Investment securities, available-for-sale	123,126	132,975
Mortgage-backed securities - Federal agencies
Assets:
Investment securities, available-for-sale	276,857	252,574
Corporate debt securities
Assets:
Investment securities, available-for-sale	31,479	35,076
Foreign government and other securities
Assets:
Investment securities, available-for-sale	202	807
Total debt securities
Assets:
Investment securities, available-for-sale	889,290	842,265
Marketable equity securities
Assets:
Investment securities, available-for-sale	4,683	8,202
Total
Assets:
Investment securities, available-for-sale	893,973	850,467
Mortgages held for sale	11,000	15,849
Level 1
Assets:
Investment securities, available-for-sale	24,916	28,366
Mortgages held for sale	0	0
Level 2
Assets:
Investment securities, available-for-sale	865,887	818,595
Mortgages held for sale	11,000	15,849
Level 3
Assets:
Investment securities, available-for-sale	3,170	3,506
Mortgages held for sale	0	0
Recurring basis \| Total
Assets:
Investment securities, available-for-sale	893,973	850,467
Mortgages held for sale	11,000	15,849
Total	910,653	872,937
Liabilities:
Total	5,785	6,743
Recurring basis \| Total \| Interest rate swap contracts
Assets:
Accrued income and other assets	5,680	6,621
Liabilities:
Accrued expenses and other liabilities	5,785	6,743
Recurring basis \| Total \| U.S. Treasury and Federal agencies securities
Assets:
Investment securities, available-for-sale	457,626	420,833
Recurring basis \| Total \| U.S. States and political subdivisions securities
Assets:
Investment securities, available-for-sale	123,126	132,975
Recurring basis \| Total \| Mortgage-backed securities - Federal agencies
Assets:
Investment securities, available-for-sale	276,857	252,574
Recurring basis \| Total \| Corporate debt securities
Assets:
Investment securities, available-for-sale	31,479	35,076
Recurring basis \| Total \| Foreign government and other securities
Assets:
Investment securities, available-for-sale	202	807
Recurring basis \| Total \| Total debt securities
Assets:
Investment securities, available-for-sale	889,290	842,265
Recurring basis \| Total \| Marketable equity securities
Assets:
Investment securities, available-for-sale	4,683	8,202
Recurring basis \| Level 1
Assets:
Investment securities, available-for-sale	24,916	28,366
Mortgages held for sale	0	0
Total	24,916	28,366
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	20,233	20,164
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	20,233	20,164
Recurring basis \| Level 1 \| Marketable equity securities
Assets:
Investment securities, available-for-sale	4,683	8,202
Recurring basis \| Level 2
Assets:
Investment securities, available-for-sale	865,887	818,595
Mortgages held for sale	11,000	15,849
Total	882,567	841,065
Liabilities:
Total	5,785	6,743
Recurring basis \| Level 2 \| Interest rate swap contracts
Assets:
Accrued income and other assets	5,680	6,621
Liabilities:
Accrued expenses and other liabilities	5,785	6,743
Recurring basis \| Level 2 \| U.S. Treasury and Federal agencies securities
Assets:
Investment securities, available-for-sale	437,393	400,669
Recurring basis \| Level 2 \| U.S. States and political subdivisions securities
Assets:
Investment securities, available-for-sale	120,158	130,276
Recurring basis \| Level 2 \| Mortgage-backed securities - Federal agencies
Assets:
Investment securities, available-for-sale	276,857	252,574
Recurring basis \| Level 2 \| Corporate debt securities
Assets:
Investment securities, available-for-sale	31,479	35,076
Recurring basis \| Level 2 \| Foreign government and other securities
Assets:
Investment securities, available-for-sale	0	0
Recurring basis \| Level 2 \| Total debt securities
Assets:
Investment securities, available-for-sale	865,887	818,595
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	3,170	3,506
Mortgages held for sale	0	0
Total	3,170	3,506
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	2,968	2,699
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	202	807
Recurring basis \| Level 3 \| Total debt securities
Assets:
Investment securities, available-for-sale	3,170	3,506
Recurring basis \| Level 3 \| Marketable equity securities
Assets:
Investment securities, available-for-sale	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
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