CONDENSED BALANCE SHEETS CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Common stock par value (in dollars per share)	$ 0.01	$ 0.01
Common stock shares authorized (in shares)	140,000,000	140,000,000
Common stock shares issued (in shares)	53,444,810	53,442,532
Common stock shares outstanding (in shares)	53,444,810	53,442,532
Preferred stock par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock shares authorized (in shares)	10,000,000	10,000,000
Preferred stock shares issued (in shares)	0	0
Preferred stock shares outstanding (in shares)	0	0