Reserve for Known and Incurred but Not Reported Claims (Narrative) (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Insurance [Abstract]
Provision for title loss, percentage of title premiums and escrow fees	4.00%	4.00%
Ultimate loss rate	4.00%	4.00%
Estimated increase in loss reserve for prior policy years	$ 0	$ 0