CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	107,600,000	107,400,000
Treasury stock	6,100,000	4,200,000