Earnings Per Share - Summary of Number of Participating Securities and Earning Allocated to those Securities (Detail) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Number of participating securities	1.1	1.0	1.1	1.0