CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for receivables	$ 35,710	$ 33,882
Class A Common Stock
Class of Stock [Line Items]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	31,554,489	31,502,448
Class B Common Stock
Class of Stock [Line Items]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	555,556	555,556
Class C Common Stock
Class of Stock [Line Items]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	58,967,502	58,967,502
Class D Common Stock
Class of Stock [Line Items]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	0	0
Treasury stock
Class of Stock [Line Items]
Treasury stock, shares	391,412	389,920