Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Equity:
Common stock, par value (usd per share)	$ 0.001	$ 0.001
Common stock, shares authorized (shares)	300,000,000	300,000,000
Common stock, shares outstanding (shares)	141,040,038	139,627,375