Consolidated Balance Sheets (parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 0	$ 0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	49,513,528	49,092,260
Common stock, shares outstanding	49,513,528	49,092,260