Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Property and equipment, accumulated depreciation	$ 32,612	$ 28,149
Intangible assets, accumulated amortization	4,276	$ 3,852
Right of use asset, accumulated amortization	$ 1,491
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	3,333,333	3,333,333
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	99,000,000	99,000,000
Common stock, issued	74,133,521	71,071,887
Common stock, outstanding	74,133,521	71,071,887