Investment Securities - Portfolio of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 362,946
Unrealized Gains	823
Unrealized Losses	11,163
Fair Value	352,606
Amortized Cost		$ 312,584
Unrealized Gains		1,961
Unrealized Losses		5,354
Fair Value		309,191
Obligations of state and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	23,775
Unrealized Gains	27
Unrealized Losses	1,043
Fair Value	22,759
Amortized Cost		23,042
Unrealized Gains		209
Unrealized Losses		442
Fair Value		22,809
GSE mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	313,605
Unrealized Gains	468
Unrealized Losses	10,028
Fair Value	304,045
Collateralized mortgage obligations: residential
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		263,467
Unrealized Gains		915
Unrealized Losses		4,863
Fair Value		259,519
Mutual funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		2,100
Unrealized Gains		0
Unrealized Losses		39
Fair Value		2,061
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	25,566
Unrealized Gains	328
Unrealized Losses	92
Fair Value	$ 25,802
Amortized Cost		23,975
Unrealized Gains		837
Unrealized Losses		10
Fair Value		$ 24,802

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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