CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	45,895,086	45,124,948
Common stock, shares outstanding (in shares)	33,865,688	34,394,412
Treasury stock, shares (in shares)	12,029,398	10,730,536