Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	90,000,000	90,000,000
Common stock, shares issued	62,830,000	61,897,000
Common stock, shares outstanding	62,552,000	61,619,000