CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts receivable, allowance for doubtful accounts	$ 0	$ 801
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, issued	0	0
Common stock, par value
Common Stock, shares authorized	200,000,000	200,000,000
Common stock, issued	82,964,314	83,634,955
Common stock, outstanding	82,964,314	83,634,955
Treasury stock, common shares	880,435	510,923
Restricted Stock
Common stock, issued	691,488	669,554
Common stock, outstanding	691,488	669,554