Amounts of Gross Realized Capital Gains and Gross Realized Capital Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Gross realized capital gains	$ 11,200	$ 20,900
Gross realized capital losses	(21,200)	(8,000)
Net realized capital gains	$ (10,003)	$ 12,931