Supplemental Disclosures of Cash Flow Information - Summary of Noncash Transactions (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Supplemental Cash Flow Elements [Abstract]
Stock-based compensation not involving cash	$ 30,272	$ 35,892	$ 44,843
Commitments for low-income housing interests	177,010	161,503	51,978
Exchanges of fixed maturity investments	109,226	219,807	243,156
Net unsettled security trades	6,963	1,669	8,421
Noncash tax credits	$ 1,883	$ 0	$ 0