Fair Value - Change in Fair Value for All Assets and Liabilities Using Unobservable Level 3 Inputs As Determined By Level 3 Inputs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock Warrants [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 14,090
Issuance of warrants		$ 8,715
Exercise of warrants	(23,774)	(78,359)
Change in fair value	14,320	83,734
Long-term portion	4,636
Ending balance	4,636	14,090
Contingent Consideration [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	12,418	22,800	$ 23,500
Issuance of common stock in exchange for contingent consideration		(5,227)
Payment for contingent consideration	(770)	(7,181)	(1,182)
Change in fair value	(1,011)	2,026	482
Current portion	72
Long-term portion	10,565
Ending balance	$ 10,637	$ 12,418	$ 22,800