Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable, allowances	$ 21,897	$ 17,739
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	1,150,000,000	1,150,000,000
Common stock, shares issued	109,770,000	99,157,000
Common stock, shares outstanding	109,770,000	99,157,000
Class A Common Stock
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	77,820,000	19,325,000
Common stock, shares outstanding	77,820,000	19,325,000
Class B Common Stock
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	31,950,000	79,832,000
Common stock, shares outstanding	31,950,000	79,832,000