CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000	5,000
Preferred stock, shares issued	5,000	5,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	355,300,000	355,300,000
Common stock, shares outstanding	355,300,000	355,300,000
Treasury stock, shares	13,200,000	13,200,000