Investments - Realized Gain (Loss) on Investments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Realized (gains) losses	$ (12,256)	$ 16,269	$ (30,128)	$ 32,578
Provision for credit losses	0	0	387	3,346
Fair value option—change in fair value	(11,551)	1,585	(15,942)	14,013
Other investments	(5,348)	1,935	(21,162)	6,663
Realized gains (losses) from investments	(29,155)	19,789	(66,845)	56,600
Realized loss—redemption of debt	0	(9,314)	0	(9,314)
Total realized gains (losses)	(29,155)	10,475	(66,845)	47,286
Applicable tax	6,122	(2,200)	14,037	(9,930)
Realized gains (losses), net of tax	(23,033)	8,275	(52,808)	37,356
Exchanges of fixed maturities	22,100	0	24,000	108,300
Exchanges of fixed maturities, net realized gains	$ 0	$ 0	$ 0	$ 25,200