CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 0	$ 0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, shares authorized (in shares)	100,000,000	100,000,000
Common Stock, shares issued (in shares)	35,921,267	35,555,562
Common Stock, shares outstanding (in shares)	29,234,577	28,917,559
Treasury Stock, shares (in shares)	6,686,690	6,638,003