CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
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	199,300,000	199,300,000
Class A common stock, shares issued	100,421,000	99,301,000
Class A common stock, shares outstanding	85,240,000	84,395,000
Treasury stock, at cost, shares held	15,181,000	14,906,000