Other Comprehensive Income (Loss) - Schedule of Activity in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances at Beginning	$ 657,677	$ 590,649	$ 620,871	$ 576,202
Other comprehensive income (loss)	3,323	(5,501)	26,314	(23,706)
Balances at Ending	659,865	599,144	659,865	599,144
Available-for- Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances at Beginning	(1,223)	(31,800)	(23,589)	(13,005)
Other comprehensive income (loss) before reclassifications	3,111	(5,806)	25,681	(24,444)
Amounts reclassified from accumulated other comprehensive (loss) income	(101)	(23)	(305)	(245)
Other comprehensive income (loss)	3,010	(5,829)	25,376	(24,689)
Balances at Ending	1,787	(37,629)	1,787	(37,629)
Employee Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances at Beginning	(38,951)	(37,636)	(39,576)	(38,291)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive (loss) income	313	328	938	983
Other comprehensive income (loss)	313	328	938	983
Balances at Ending	(38,638)	(37,308)	(38,638)	(37,308)
Accumulated Other Comprehensive (Loss) Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances at Beginning	(40,174)	(69,436)	(63,165)	(51,296)
Other comprehensive income (loss) before reclassifications	3,111	(5,806)	25,681	(24,444)
Amounts reclassified from accumulated other comprehensive (loss) income	212	305	633	738
Other comprehensive income (loss)	3,323	(5,501)	26,314	(23,706)
Balances at Ending	$ (36,851)	$ (74,937)	$ (36,851)	$ (74,937)
Accounting Standards Update 2016-01
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect of new accounting principle					$ 0
Accounting Standards Update 2016-01 \| Available-for- Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect of new accounting principle					65
Accounting Standards Update 2016-01 \| Employee Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect of new accounting principle					0
Accounting Standards Update 2016-01 \| Accumulated Other Comprehensive (Loss) Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect of new accounting principle					$ 65

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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