Other Comprehensive Income (Loss) - Amounts reclassified from accumulated other comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Provision for credit losses	$ 8,652	$ (456)	$ (48,096)	$ (1,208)
Income tax expense	14,900	(4,137)	(19,042)	(94,176)
Net of tax	18,258	421,415	619,635	1,615,787
Reclassification out of accumulated other comprehensive income | Unrealized appreciation on available-for-sale investments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses)	(55,940)	68,373	(186,570)	135,291
Provision for credit losses	8,652	(457)	(48,096)	(1,208)
Income (loss) before income taxes and income (loss) from operating affiliates	(47,288)	67,916	(234,666)	134,083
Income tax expense	703	(5,262)	28,093	(13,579)
Net of tax	$ (46,585)	$ 62,654	$ (206,573)	$ 120,504