Reserve for Known and Incurred but Not Reported Claims (Summary of Loss Reserves) (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Insurance [Abstract]
Known title claims, amount	$ 62,884	$ 64,601
Incurred but not reported claims, amount	1,049,835	1,025,761
Total title claims, amount	1,112,719	1,090,362
Non-title claims, amount	90,450	87,642
Total loss reserves, amount	$ 1,203,169	$ 1,178,004	$ 1,057,538	$ 1,063,044
Known title claims, percent	5.20%	5.50%
Incurred but not reported claims, percent	87.30%	87.10%
Total title claims, percent	92.50%	92.60%
Non-title claims, percent	7.50%	7.40%
Total loss reserves, percent	100.00%	100.00%