Earnings Per Share - Summary of Number of Participating Securities and Earning Allocated to those Securities (Detail) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Number of participating securities	1.1	0.9	1.1	1.0