Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2017	Dec. 31, 2016
Condensed Consolidated Balance Sheets
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	50,000,000
Common stock, shares issued (in shares)	46,976,898	45,895,086
Common stock, shares outstanding (in shares)	33,607,808	33,865,688
Treasury stock, shares (in shares)	13,369,090	12,029,398