Consolidated Balance Sheets (unaudited) (Parenthetical) - $ / shares	Jun. 30, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	59,520,637	58,453,283
Common stock, shares outstanding	57,938,217	57,331,022
Treasury stock, shares	1,582,420	1,122,261