Fair Value (Details 1) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Fair value measurement using significant unobservable input
Securities available-for-sale	$ 805,558	$ 814,931
Reconciliation and income statement classification of gains and losses for all assets measured at fair value on a recurring basis using significant unobservable inputs
Beginning balance	18,285	16,578
Total realized/unrealized gains or losses - Included in earnings	0	0
Total realized/unrealized gains or losses - Included in other comprehensive income	1,073	2,773
Transfers	0
Purchases		0
Settlements	(693)	(1,066)
Ending balance	18,665	18,285
US Government Agencies Debt Securities [Member]
Fair value measurement using significant unobservable input
Securities available-for-sale	13,402	13,695
State and Municipal Obligations
Fair value measurement using significant unobservable input
Securities available-for-sale	227,889	231,622
Reconciliation and income statement classification of gains and losses for all assets measured at fair value on a recurring basis using significant unobservable inputs
Beginning balance	3,680	4,210
Total realized/unrealized gains or losses - Included in earnings	0	0
Total realized/unrealized gains or losses - Included in other comprehensive income	0	0
Transfers	0
Purchases		0
Settlements	(545)	(530)
Ending balance	3,135	3,680
Collateralized Debt Obligations
Fair value measurement using significant unobservable input
Securities available-for-sale	15,530	14,605
Reconciliation and income statement classification of gains and losses for all assets measured at fair value on a recurring basis using significant unobservable inputs
Beginning balance	14,605	12,368
Total realized/unrealized gains or losses - Included in earnings	0	0
Total realized/unrealized gains or losses - Included in other comprehensive income	1,073	2,773
Transfers	0
Purchases		0
Settlements	(148)	(536)
Ending balance	15,530	14,605
Mortgage Backed Securities - Residential
Fair value measurement using significant unobservable input
Securities available-for-sale	201,607	215,338
Mortgage Backed Securities - Commercial
Fair value measurement using significant unobservable input
Securities available-for-sale	0	1
Collateralized Mortgage Obligations
Fair value measurement using significant unobservable input
Securities available-for-sale	347,130	339,670
Fair Value, Inputs, Level 3 [Member]
Fair value measurement using significant unobservable input
Securities available-for-sale	18,665	18,285
Fair Value, Inputs, Level 3 [Member] \| US Government Agencies Debt Securities [Member]
Fair value measurement using significant unobservable input
Securities available-for-sale	0	0
Fair Value, Inputs, Level 3 [Member] \| State and Municipal Obligations
Fair value measurement using significant unobservable input
Securities available-for-sale	3,135	3,680
Fair Value, Inputs, Level 3 [Member] \| Collateralized Debt Obligations
Fair value measurement using significant unobservable input
Securities available-for-sale	15,530	14,605
Fair Value, Inputs, Level 3 [Member] \| Mortgage Backed Securities - Residential
Fair value measurement using significant unobservable input
Securities available-for-sale	0	0
Fair Value, Inputs, Level 3 [Member] \| Mortgage Backed Securities - Commercial
Fair value measurement using significant unobservable input
Securities available-for-sale	0	0
Fair Value, Inputs, Level 3 [Member] \| Collateralized Mortgage Obligations
Fair value measurement using significant unobservable input
Securities available-for-sale	0	0
Fair Value, Inputs, Level 1 [Member]
Fair value measurement using significant unobservable input
Securities available-for-sale	0	0
Fair Value, Inputs, Level 1 [Member] \| US Government Agencies Debt Securities [Member]
Fair value measurement using significant unobservable input
Securities available-for-sale	0	0
Fair Value, Inputs, Level 1 [Member] \| State and Municipal Obligations
Fair value measurement using significant unobservable input
Securities available-for-sale	0	0
Fair Value, Inputs, Level 1 [Member] \| Collateralized Debt Obligations
Fair value measurement using significant unobservable input
Securities available-for-sale	0	0
Fair Value, Inputs, Level 1 [Member] \| Mortgage Backed Securities - Residential
Fair value measurement using significant unobservable input
Securities available-for-sale	0	0
Fair Value, Inputs, Level 1 [Member] \| Mortgage Backed Securities - Commercial
Fair value measurement using significant unobservable input
Securities available-for-sale	0	0
Fair Value, Inputs, Level 1 [Member] \| Collateralized Mortgage Obligations
Fair value measurement using significant unobservable input
Securities available-for-sale	0	0
Fair Value, Inputs, Level 2 [Member]
Fair value measurement using significant unobservable input
Securities available-for-sale	786,893	796,646
Reconciliation and income statement classification of gains and losses for all assets measured at fair value on a recurring basis using significant unobservable inputs
Derivative Assets	295	298
Derivative Liability	295	298
Fair Value, Inputs, Level 2 [Member] \| US Government Agencies Debt Securities [Member]
Fair value measurement using significant unobservable input
Securities available-for-sale	13,402	13,695
Fair Value, Inputs, Level 2 [Member] \| State and Municipal Obligations
Fair value measurement using significant unobservable input
Securities available-for-sale	224,754	227,942
Fair Value, Inputs, Level 2 [Member] \| Collateralized Debt Obligations
Fair value measurement using significant unobservable input
Securities available-for-sale	0	0
Fair Value, Inputs, Level 2 [Member] \| Mortgage Backed Securities - Residential
Fair value measurement using significant unobservable input
Securities available-for-sale	201,607	215,338
Fair Value, Inputs, Level 2 [Member] \| Mortgage Backed Securities - Commercial
Fair value measurement using significant unobservable input
Securities available-for-sale	0	1
Fair Value, Inputs, Level 2 [Member] \| Collateralized Mortgage Obligations
Fair value measurement using significant unobservable input
Securities available-for-sale	$ 347,130	$ 339,670

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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