Investments - Schedule of Available-for-sale and Held-to-Maturity Securities Reconciliation (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 73,749	$ 80,463
Gross Unrealized Gains	85	56
Gross Unrealized Losses	(376)	(880)
Fair Value	73,458	79,639
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	647,141	463,143
Gross Unrealized Gains	1,407	2,079
Gross Unrealized Losses	(7,166)	(4,425)
Fair Value	641,382	460,797
Obligations of U.S. Government-sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	99,878	107,312
Gross Unrealized Gains	6	348
Gross Unrealized Losses	(660)	0
Fair Value	99,224	107,660
Obligations of states and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	34,181	36,486
Gross Unrealized Gains	674	630
Gross Unrealized Losses	(213)	(485)
Fair Value	34,642	36,631
Residential mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	513,082	319,345
Gross Unrealized Gains	727	1,101
Gross Unrealized Losses	(6,293)	(3,940)
Fair Value	507,516	316,506
Obligations of states and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	14,031	14,759
Gross Unrealized Gains	69	11
Gross Unrealized Losses	(46)	(242)
Fair Value	14,054	14,528
Residential mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	59,718	65,704
Gross Unrealized Gains	16	45
Gross Unrealized Losses	(330)	(638)
Fair Value	$ 59,404	$ 65,111

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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