Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax		$ (35,305)	$ (22,225)	$ (18,999)	$ (6,295)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		(13,401)	626	(12,377)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	164	230	(327)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		(13,237)	856	(12,704)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(33,128)	(19,779)	(12,704)	386
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		(13,425)	(3,391)	(12,338)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	(81)	7	(752)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		(13,506)	(3,384)	(13,090)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(2,177)	(2,446)	(6,295)	$ (6,681)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax		24	4,017	(39)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	245	223	425
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		$ 269	4,240	386
Accounting Standards Update 2016-01 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			0
Accounting Standards Update 2016-01 [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			157
Accounting Standards Update 2016-01 [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			0
Accounting Standards Update 2016-01 [Member] | Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			157
Accounting Standards Update 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption				0
Accounting Standards Update 2018-02 [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			(3,691)
Accounting Standards Update 2018-02 [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			(391)
Accounting Standards Update 2018-02 [Member] | Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			$ (4,082)	$ (4,082)

[1] See following table for details about these reclassifications.