Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Stockholders' equity (deficit)
Allowance for doubtful accounts	$ 3,457	$ 3,537
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, authorized	20,000,000	20,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common Class A
Stockholders' equity (deficit)
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized	250,000,000	250,000,000
Common stock, issued	38,018,386	37,701,584
Common stock, outstanding	37,773,109	37,488,989
Common Class B
Stockholders' equity (deficit)
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, authorized	75,000,000	75,000,000
Common stock, issued	69,066,445	69,066,445
Common stock, outstanding	50,706,629	50,706,629
Common Class C
Stockholders' equity (deficit)
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, authorized	1	1
Common stock, issued	1	1
Common stock, outstanding	1	1