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Investments - Schedule of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized cost	$ 385,833	$ 388,520
Gross unrealized gains	235	2,486
Gross unrealized losses	(10,029)	(3,023)
Estimated fair value	376,039	387,983
US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized cost	1,999	1,999
Gross unrealized gains
Gross unrealized losses	(56)	(9)
Estimated fair value	1,943	1,990
US Federal Agency Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized cost	15,177	16,572
Gross unrealized gains	2	5
Gross unrealized losses	(90)	(85)
Estimated fair value	15,089	16,492
Municipal Obligations, Tax Exempt [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized cost	161,474	183,846
Gross unrealized gains	148	1,972
Gross unrealized losses	(4,365)	(1,080)
Estimated fair value	157,257	184,738
Municipal Obligations, Taxable [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized cost	53,834	57,783
Gross unrealized gains	81	409
Gross unrealized losses	(924)	(216)
Estimated fair value	52,991	57,976
Agency Mortgage-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized cost	145,569	119,096
Gross unrealized gains	4	92
Gross unrealized losses	(4,594)	(1,633)
Estimated fair value	140,979	117,555
Certificates of Deposit [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized cost	7,780	9,224
Gross unrealized gains
Gross unrealized losses
Estimated fair value	$ 7,780	9,224
Common Stocks [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized cost
Gross unrealized gains		8
Gross unrealized losses
Estimated fair value		$ 8

X

- Definition

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

+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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- Definition

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

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