Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 4,574	$ 3,664
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	30,000,000	30,000,000
Preferred stock, shares issued	0
Preferred stock, shares outstanding	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	187,500,000	187,500,000
Common stock, shares issued	124,008,303	112,547,544
Common stock, shares outstanding	124,008,303	112,547,544