CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Accounts receivable, allowance for doubtful accounts	$ 4,575	$ 4,246
Total assets of variable interest entities	162,300	163,300
Total liabilities of variable interest entities	$ 39,600	$ 30,000
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	68,762,925	69,578,899
Common Stock, shares outstanding	68,762,925	69,578,899
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	25,928,357	25,928,357
Common Stock, shares outstanding	25,928,357	25,928,357