Investments, Major Categories of Investment Income (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investment Income, Net [Abstract]
Investment Income	$ 27,812	$ 28,916	$ 25,001
Investment expenses	(2,390)	(2,667)	(2,953)
Net investment income	25,422	26,249	22,048
Interest on Fixed Income Securities [Member]
Investment Income, Net [Abstract]
Investment Income	24,874	24,620	19,092
Dividends on Equity Securities [Member]
Investment Income, Net [Abstract]
Investment Income	1,868	2,320	4,380
Money Market Funds, Short term and Other [Member]
Investment Income, Net [Abstract]
Investment Income	$ 1,070	$ 1,976	$ 1,529

Amount before accretion (amortization) of purchase discount (premium) of interest income and dividend income on nonoperating securities.

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Amount of expenses related to the generation of investment income.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.2)
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

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Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7(a),(b))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

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