Supplemental Disclosure of Noncash Investing and Financing Activities - Supplemental Disclosure of Noncash Investing and Financing Activities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investing activities:
Acquisition-related contingent consideration		$ 10,611	$ 514
Common stock issued in connection with the acquisition		2,764
Capital expenditures incurred not yet paid	$ 344	755	835
Capital expenditure milestone payable incurred not yet paid			4,609
Stock-based compensation included in capital expenditures	502	453	314
Financing activities:
Common stock issued as form of payment for MPUs	827
Common stock issued as payment for contingent consideration		347	352
Series A convertible preferred stock dividend paid-in-kind	$ 18	$ 12	$ 14