CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Class A common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Class A common stock, shares authorized (in shares)	199,300,000.0	199,300,000.0
Class A common stock, shares issued (in shares)	104,700,000	103,700,000
Class A common stock, shares outstanding (in shares)	87,500,000	86,500,000
Treasury stock, at cost, shares held (in shares)	17,200,000	17,200,000