Stockholders' Equity and Share-Based Awards - Additional Information (Detail) shares in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($) shares
Performance-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock units awarded | shares	1.4
Aggregate grant date fair value | $	$ 65.6
Time-Based RSU's [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock units awarded | shares	0.5
Aggregate grant date fair value | $	$ 23.4