Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Stockholders' equity
Allowance for doubtful accounts	$ 2,920	$ 2,929
Preferred stock par value	$ 0.01
Preferred stock authorized	20,000,000
Preferred stock, issued	0
Preferred stock, outstanding	0
Class A common stock
Stockholders' equity
Common stock, par value	$ 0.01
Common stock, authorized	250,000,000
Common stock, issued	18,935,916
Common stock, outstanding	18,935,916
Class B common stock
Stockholders' equity
Common stock, par value	$ 0.0001
Common stock, authorized	75,000,000
Common stock, issued	69,066,445
Common stock, outstanding	62,002,729
Class C common stock
Stockholders' equity
Common stock, par value	$ 0.0001
Common stock, authorized	1
Common stock, issued	1
Common stock, outstanding	1