Segment and Geographic Data (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment	1
Revenue, Major Customer [Line Items]
Revenue	$ 476.2	$ 293.3	$ 144.3
United States
Revenue, Major Customer [Line Items]
Revenue	433.2	267.3	134.9
Rest of world
Revenue, Major Customer [Line Items]
Revenue	$ 43.0	$ 26.0	$ 9.4
Rest of world | Geographic Concentration Risk | Revenue from Contract with Customer Benchmark
Revenue, Major Customer [Line Items]
Concentration risk (as a percent)	9.00%	9.00%	7.00%