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Investments (Aggregated Income Statement Summarized Financial Information for Partnerhips in our Alternative Investment Portfolio) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Net investment income earned	$ 83,731	$ 34,444	$ 153,447	$ 90,411
Carrying Value	330,479		330,479		$ 266,322
Alternative Investments [Member]
Schedule of Equity Method Investments [Line Items]
Net investment income earned	29,900	(16,000)	50,100	(9,700)
Investments accounted for under the equity method [Member]
Schedule of Equity Method Investments [Line Items]
Net investment income	8,400	(3,100)	490,000	9,600
Realized gains	1,392,500	179,000	2,168,600	343,800
Net change in unrealized appreciation	4,948,900	(2,862,900)	9,579,700	(1,658,900)
Insurance Subsidiaries' alternative investments income	$ 6,349,800	$ (2,687,000)	$ 12,238,300	$ (1,305,500)

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
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-Topic 944
-SubTopic 210
-Section S99
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