Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Common stock, number of shares outstanding (in shares)	77,881,873	77,525,973
Common Stock
Common stock, par value (in USD per share)	$ 0.001	$ 0.001
Common stock, number of shares authorized (in shares)	800,000,000	800,000,000
Common stock, number of shares outstanding (in shares)	77,881,873	77,525,973