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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		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Net investment income earned	$ 93,032	$ 68,185	$ 246,479	$ 158,596
Carrying Value	392,788		392,788		$ 266,322
Alternative Investments [Member]
Schedule of Equity Method Investments [Line Items]
Net investment income earned	42,800	18,700	92,900	8,900
Investments accounted for under the equity method [Member]
Schedule of Equity Method Investments [Line Items]
Net investment income	60,400	83,400	550,300	92,900
Realized gains	1,857,600	731,300	4,026,200	1,075,000
Net change in unrealized appreciation	11,188,200	2,230,400	20,767,900	571,600
Insurance Subsidiaries' alternative investments income	$ 13,106,200	$ 3,045,100	$ 25,344,400	$ 1,739,500

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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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