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Description of the Business and Summary of Significant Accounting Policies - Stock-based Compensation (Details) - shares shares in Millions		1 Months Ended	6 Months Ended	12 Months Ended
	Mar. 19, 2020	Dec. 31, 2017	Jun. 30, 2020	Dec. 31, 2019
One-Tier RSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)			20.8
Shares forfeited (in shares)			5.8
Tranche One \| One-Tier RSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			1 year
Co-Founder Grants \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)		14.7	10.3	14.7
Shares forfeited (in shares)	4.4
Co-Founder Grants \| Tranche One \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		4 years
Chief Executive Officer \| Co-Founder Grants \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)		10.3
Director \| Co-Founder Grants \| Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)		4.4
Shares forfeited (in shares)	4.4