CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 4,495	$ 4,246
Total assets of variable interest entities (in dollars)	152,400	163,300
Total liabilities of variable interest entities (in dollars)	$ 35,600	$ 30,000
Class A Common Stock
Common Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, shares authorized (in shares)	500,000,000	500,000,000
Common Stock, shares issued (in shares)	68,792,483	69,578,899
Common Stock, shares outstanding (in shares)	68,792,483	69,578,899
Class B Common Stock
Common Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, shares authorized (in shares)	140,000,000	140,000,000
Common Stock, shares issued (in shares)	25,928,357	25,928,357
Common Stock, shares outstanding (in shares)	25,928,357	25,928,357