CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Allowance for receivables	$ 33,882	$ 34,889
Common Class A
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	31,502,448	30,295,457
Common Class B
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
Common Class C
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
Treasury Stock
Class of Stock [Line Items]
Treasury stock, shares	389,920	229,824