Income taxes - rate reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Rate reconciliation
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	$ 851.1	$ 753.0	$ 62.3
United States federal corporate rate	21.00%	21.00%	21.00%
Income tax expense at federal corporate rate	$ (178.7)	$ (158.2)	$ (13.1)
State income taxes, net of federal benefit	(23.3)	(27.0)	7.6
Rate changes related to foreign jurisdictions	1.3	(9.7)	(4.0)
Stock-based compensation	3.5	14.5	10.1
Foreign taxes	12.8	1.4	5.7
Valuation allowance	4.8	4.1	(1.1)
Changes to uncertain tax positions	1.1	(10.7)	40.8
Foreign-derived intangible income	12.1	8.2	6.9
Transaction costs	0.0	(2.1)	0.0
Other, net	1.8	(0.9)	1.4
Income tax (expense) benefit	$ (164.6)	$ (180.4)	$ 54.3

Effective Income Tax Rate Reconciliation, Foreign-derived Intangible Income

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Amount of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to expense for award under share-based payment arrangement. Excludes expense determined to be nondeductible upon grant or after for award under share-based payment arrangement.

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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