Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable reserve	$ 1,065	$ 1,281
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares designated as Series A Junior Participating Preferred Stock	700,000	700,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	700,000,000	700,000,000
Common stock, shares issued	171,763,861	169,893,324
Common stock, shares outstanding	169,311,093	169,893,324
Treasury stock, shares	2,452,768	0