Other Comprehensive Income (Loss) - Amounts reclassified from accumulated other comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Provision for credit losses	$ (25,026)	$ 896	$ (56,748)	$ (752)
Income tax expense	(22,323)	(51,179)	(33,942)	(90,039)
Net of tax	403,945	718,664	601,377	1,194,372
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)	(41,990)	64,914	(130,630)	66,918
Provision for credit losses	(25,026)	896	(56,748)	(751)
Income (loss) before income taxes and income (loss) from operating affiliates	(67,016)	65,810	(187,378)	66,167
Income tax expense	9,306	(5,263)	27,390	(8,317)
Net of tax	$ (57,710)	$ 60,547	$ (159,988)	$ 57,850