Investments - Realized Gain (Loss) on Investments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Sales and other	$ (22,421)	$ 865	$ (17,872)	$ 16,309
Provision for credit losses	0	0	387	3,346
Fair value option—change in fair value	947	2,543	(4,391)	12,428
Other investments	(8,972)	5,251	(15,814)	4,728
Realized gains (losses) from investments	(30,446)	8,659	(37,690)	36,811
Applicable tax	6,394	(1,818)	7,915	(7,730)
Realized gains (losses), net of tax	(24,052)	6,841	(29,775)	29,081
Exchanges of fixed maturities	1,900	22,400	1,900	108,300
Exchanges of fixed maturities, net realized gains	$ 0	$ 0	$ 0	$ 25,200