Significant Consolidated Balance Sheet Components - Property, Equipment and Software (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total property, equipment and software	$ 82.0	$ 59.2
Accumulated depreciation and amortization	(47.1)	(31.5)
Total property, equipment and software — net	34.9	27.7
Capitalized software development costs	24.2	19.2	$ 15.2
Amortization of capitalized software	16.7	12.5	8.2
Impairment of capitalized software development costs	0.8	0.2	1.1
Depreciation and amortization expense excluding capitalized software	2.4	1.0	$ 1.2
Capitalized software development costs
Property, Plant and Equipment [Line Items]
Total property, equipment and software	71.6	51.7
Office equipment
Property, Plant and Equipment [Line Items]
Total property, equipment and software	5.3	4.1
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property, equipment and software	1.4	1.0
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property, equipment and software	$ 3.7	$ 2.4