Disaggregated Revenue (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Revenues	$ 4,590.7	$ 4,284.2	$ 3,679.6
Total service revenue
Disaggregation of Revenue [Line Items]
Revenues	3,502.2	3,363.6	2,732.5
Transactional seller revenue
Disaggregation of Revenue [Line Items]
Revenues	928.8	939.4	851.7
Transactional buyer revenue
Disaggregation of Revenue [Line Items]
Revenues	2,238.3	2,067.1	1,593.2
Marketplace services revenue
Disaggregation of Revenue [Line Items]
Revenues	335.1	357.1	287.6
Inventory sales revenue
Disaggregation of Revenue [Line Items]
Revenues	$ 1,088.5	$ 920.6	$ 947.1