CONSOLIDATED BALANCE SHEETS (PARENTHETICAL) - USD ($) shares in Thousands, $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	20,000	20,000
Preferred Stock, Shares Outstanding	0	0
Current assets
Allowance for doubtful accounts	$ 1,863	$ 3,181
Stockholders' equity
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	240,000	240,000
Common stock, shares issued	83,026	81,989
Common stock, shares outstanding	50,417	49,591
Treasury stock, shares	32,609	32,398