Investments (Rollforward of Allowance for Credit Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Beginning balance	$ 2,846	$ 64,771
Additions for credit losses not previously recorded	4,161	816
Change in allowance on securities with previous allowance	(430)	621
Reduction for securities sold during the period	0	(6,510)
Ending balance	6,577	59,698
United States Municipalities, States and Territories
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Beginning balance	2,776	2,844
Additions for credit losses not previously recorded	0	0
Change in allowance on securities with previous allowance	(767)	(53)
Reduction for securities sold during the period	0	0
Ending balance	2,009	2,791
Corporate Securities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Beginning balance	0	60,193
Additions for credit losses not previously recorded	3,825	705
Change in allowance on securities with previous allowance	0	1,327
Reduction for securities sold during the period	0	(6,510)
Ending balance	3,825	55,715
Commercial Mortgage Backed Securities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Beginning balance	0	0
Additions for credit losses not previously recorded	0	0
Change in allowance on securities with previous allowance	0	0
Reduction for securities sold during the period	0	0
Ending balance	0	0
Residential Mortgage Backed Securities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Beginning balance	70	1,734
Additions for credit losses not previously recorded	336	111
Change in allowance on securities with previous allowance	337	(653)
Reduction for securities sold during the period	0	0
Ending balance	743	1,192
Other Asset Backed Securities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Beginning balance	0	0
Additions for credit losses not previously recorded	0	0
Change in allowance on securities with previous allowance	0	0
Reduction for securities sold during the period	0	0
Ending balance	$ 0	$ 0

Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124269663&loc=SL82922900-210455

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=124269663&loc=SL82922900-210455

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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