Summary of Significant Accounting Policies - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Liabilities
Expected volatility rate period	180 days
Minimum
Liabilities
Maximum volatility rate	40.00%
Common Stock Warrant Liabilities
Liabilities
Liabilities measured at fair value on a recurring basis	$ 1,669	$ 6,196
Contingent Purchase Consideration
Liabilities
Liabilities measured at fair value on a recurring basis	52,300	51,000
Money market fund shares
Assets
Assets measured at fair value on a recurring basis	128,959	148,588
Quoted Prices in Active Markets for Identical Assets (Level 1) | Common Stock Warrant Liabilities
Liabilities
Liabilities measured at fair value on a recurring basis	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Contingent Purchase Consideration
Liabilities
Liabilities measured at fair value on a recurring basis	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market fund shares
Assets
Assets measured at fair value on a recurring basis	128,959	148,588
Significant Other Observable Inputs (Level 2) | Common Stock Warrant Liabilities
Liabilities
Liabilities measured at fair value on a recurring basis	0	0
Significant Other Observable Inputs (Level 2) | Contingent Purchase Consideration
Liabilities
Liabilities measured at fair value on a recurring basis	0	0
Significant Other Observable Inputs (Level 2) | Money market fund shares
Assets
Assets measured at fair value on a recurring basis	0	0
Significant Unobservable Inputs (Level 3) | Common Stock Warrant Liabilities
Liabilities
Liabilities measured at fair value on a recurring basis	1,669	6,196
Significant Unobservable Inputs (Level 3) | Contingent Purchase Consideration
Liabilities
Liabilities measured at fair value on a recurring basis	52,300	51,000
Significant Unobservable Inputs (Level 3) | Money market fund shares
Assets
Assets measured at fair value on a recurring basis	$ 0	$ 0