CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Allowance for doubtful accounts	$ 4,098	$ 3,161
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	118,037,162	118,855,201
Common stock, shares outstanding (in shares)	115,869,769	116,687,808
Treasury stock (in shares)	2,167,393	2,167,393
Series B Preferred stock ($0.01 par value, 1,000,000 shares authorized, no shares issued and outstanding)
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Series C Preferred stock ($0.01 par value, 18,500 shares authorized, no shares issued and outstanding)
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	18,500	18,500
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0