Other Comprehensive Income (Loss) - Activity in AOCI (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances at Beginning	$ 647,267	$ 579,411	$ 620,871	$ 576,202
Other comprehensive income (loss)	10,776	(3,819)	22,991	(18,205)
Balances at Ending	657,677	590,649	657,677	590,649
Available-for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances at Beginning	(11,695)	(27,644)	(23,589)	(13,005)
Other comprehensive income (loss) before reclassifications	10,676	(4,028)	22,570	(18,638)
Amounts reclassified from accumulated other comprehensive (loss) income	(204)	(128)	(204)	(222)
Other comprehensive income (loss)	10,472	(4,156)	22,366	(18,860)
Balances at Ending	(1,223)	(31,800)	(1,223)	(31,800)
Employee Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances at Beginning	(39,255)	(37,973)	(39,576)	(38,291)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive (loss) income	304	337	625	655
Other comprehensive income (loss)	304	337	625	655
Balances at Ending	(38,951)	(37,636)	(38,951)	(37,636)
Accumulated Other Comprehensive (Loss) Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances at Beginning	(50,950)	(65,617)	(63,165)	(51,296)
Other comprehensive income (loss) before reclassifications	10,676	(4,028)	22,570	(18,638)
Amounts reclassified from accumulated other comprehensive (loss) income	100	209	421	433
Other comprehensive income (loss)	10,776	(3,819)	22,991	(18,205)
Balances at Ending	$ (40,174)	$ (69,436)	$ (40,174)	$ (69,436)
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 after tax and 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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