Summary of Significant Accounting Policies - Reconciliation of Liabilities Measured at Fair Value Using Significant Observable Inputs (Level 3) (Detail) - Significant Unobservable Inputs (Level 3) [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Contingent Purchase Consideration [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 51,000	$ 53,000
Additions	0	0
Changes in fair value	1,800	(2,000)
Ending Balance	52,800	51,000
Common Stock Warrant Liability [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	6,196	5,093
Additions	0
Changes in fair value	(5,387)	1,103
Ending Balance	809	6,196
Short-term Investments [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	0	0
Additions	0	11,926
Dispositions	0	(6,180)
Changes in fair value	0	(5,746)
Ending Balance	$ 0	$ 0