Share-Based Compensation - Unrecognized Compensation Expense (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($)
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	$ 50,711
Stock options
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	$ 8,005
Average Expected Recognition Period - in Years	2 years 3 months 7 days
Restricted stock units
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	$ 42,706
Average Expected Recognition Period - in Years	2 years 6 months