Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
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)	35,950,518	35,555,562
Common stock, shares outstanding (in shares)	29,263,828	28,917,559
Treasury stock, shares (in shares)	6,686,690	6,638,003