CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 3,422,000	$ 3,379,000
Total assets of variable interest entities (in dollars)	160,900,000	194,100,000
Total liabilities of variable interest entities (in dollars)	$ 35,000,000	$ 31,600,000
Class A Common Stock
Common Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, shares authorized	500,000,000	500,000,000
Common Stock, shares issued	70,466,653	74,145,569
Common Stock, shares outstanding	70,466,653	74,145,569
Class B Common Stock
Common Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, shares authorized	140,000,000	140,000,000
Common Stock, shares issued	25,978,357	26,028,357
Common Stock, shares outstanding	25,978,357	26,028,357