Comprehensive Income Changes in Accumulated Other Comprehensive Income By Component (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications	$ 0	$ 0	$ (224)
Amounts reclassified from accumulated other comprehensive income (loss)	8	7	34
Other Comprehensive Loss	(35)	1,138	(806)
Reclassification due to the adoption of ASU No. 2018-02	(1,645)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(382)	629	2,539
Other comprehensive income (loss) before reclassifications	(940)	(1,024)	(1,832)
Amounts reclassified from accumulated other comprehensive income (loss)	337	13	(78)
Other Comprehensive Loss	(603)	(1,011)	(1,910)
Reclassification due to the adoption of ASU No. 2018-02	(265)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(1,250)	(382)	629
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(5,737)	(7,893)	(9,255)
Other comprehensive income (loss) before reclassifications	214	1,721	848
Amounts reclassified from accumulated other comprehensive income (loss)	362	435	514
Other Comprehensive Loss	576	2,156	1,362
Reclassification due to the adoption of ASU No. 2018-02	(1,219)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(6,380)	(5,737)	(7,893)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit) [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(715)	(708)	(450)
Other comprehensive income (loss) before reclassifications	0	0	(224)
Amounts reclassified from accumulated other comprehensive income (loss)	(8)	(7)	(34)
Other Comprehensive Loss	(8)	(7)	(258)
Reclassification due to the adoption of ASU No. 2018-02	(161)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(884)	(715)	(708)
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(6,834)	(7,972)	(7,166)
Other comprehensive income (loss) before reclassifications	(726)	697	(1,208)
Amounts reclassified from accumulated other comprehensive income (loss)	691	441	402
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (8,514)	$ (6,834)	$ (7,972)

Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings

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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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