Share-Based Compensation - Unrecognized Share-Based Compensation Expense (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	$ 51,606
Stock options
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	16,282
Average Expected Recognition Period - in Years	2 years 7 months 19 days
Restricted stock units
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	$ 35,324
Average Expected Recognition Period - in Years	2 years 6 months 23 days