Condensed Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Millions			3 Months Ended		6 Months Ended
		Mar. 19, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reversal of stock based compensation expense		$ 23.8
Reversal of stock based compensation expense previously recognized		$ 21.5
Cost of revenue
Allocated share-based compensation expense			$ 4.5	$ 4.7	$ 8.0	$ 7.7
Research and development
Allocated share-based compensation expense			47.0	37.7	84.2	68.2
Sales and marketing
Allocated share-based compensation expense			9.5	8.8	16.2	15.9
General and administrative
Allocated share-based compensation expense	[1]		$ 15.6	$ 16.9	$ 8.0	$ 31.9

[1] On March 19, 2020, one of the Company's co-founders resigned as a member of the board and as an officer of the Company, resulting in the reversal of $23.8 million in stock-based compensation expense. Of the total amount reversed, $21.5 million related to expense recognized prior to December 31, 2019. See Note 12 "Stockholders' Equity" for further information.