Share-Based Compensation - Unrecognized Share-Based Compensation Expense (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	$ 51,552
Stock options
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	17,195
Average Expected Recognition Period - in Years	2 years 8 months
Restricted stock units
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Expense	$ 34,357
Average Expected Recognition Period - in Years	2 years 8 months 18 days