Stock-based Compensation Plans - Additional Information 3 (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 25,538,000	[1]	$ 13,954,000
Performance-based PG-PSUs and RG-PSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
Stock-based compensation expense	$ 5,300,000		6,000
Performance Based TSR - PSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
Stock-based compensation expense	$ 5,400,000		$ 3,100,000

[1] Includes $18.2 million accelerated vesting of equity grants.