Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 0	$ 15
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)	35,555,562	34,845,310
Common stock, shares outstanding (in shares)	28,917,559	28,329,416
Treasury stock, shares (in shares)	6,638,003	6,515,894