Statutory Accounting and Regulatory Requirements - Insurance Subsidiaries (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Insurance [Abstract]
Capital and surplus	$ 277,789	$ 365,524	$ 359,952
Net income	53,094	82,390	92,301
Net realized gains (losses) on investments	$ 1,695	$ 1,075	$ (80)