Summary of Significant Accounting Policies - Reconciliation of Liabilities Measured at Fair Value Using Significant Observable Inputs (Level 3) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Embedded Derivative Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Exercises		$ 0
Significant Unobservable Inputs (Level 3) [Member] | Contingent Purchase Consideration [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	0
Purchases/additions	53,000
Ending Balance	53,000
Significant Unobservable Inputs (Level 3) [Member] | Warrants and Rights Outstanding [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	31,341	9,493
Exercises	(916)	(79)
Purchases/additions	0
Changes in fair value	(25,332)	21,927
Ending Balance	5,093	31,341
Significant Unobservable Inputs (Level 3) [Member] | Embedded Derivative Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	233	992
Purchases/additions	0
Derecognition of liability	(247)
Changes in fair value	14	(759)
Ending Balance	$ 0	$ 233