Basis of presentation (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($) reporting_unit	Sep. 30, 2020 USD ($) $ / $	Sep. 30, 2021 USD ($) segment $ / $	Sep. 30, 2020 USD ($) $ / $	Dec. 31, 2020 USD ($) reporting_unit $ / $		Dec. 31, 2019 USD ($) reporting_unit $ / $		Jun. 30, 2021 USD ($)	Jan. 01, 2021 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jan. 01, 2020 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of operating segments | segment			4
Net monetary assets			$ 1,962.8		$ 1,814.8
Cash and cash equivalents			700.8		620.9
Goodwill			1,426.6		1,219.2
Argentina conversion losses			(6.6)	$ (5.3)
Provision for doubtful accounts			26.0		$ 30.7
Number of Reporting Units | reporting_unit	4				9		8
Restricted cash			321.7		$ 322.0
Cumulative effect of change in accounting principle	$ 225.1	$ 171.9	$ 249.0	$ 171.9	202.5		$ 207.6		$ 302.6		$ 190.9	$ 82.0
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle					$ 0.5	[1]	$ (1.7)	[2]
Argentina, Pesos | Argentina
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Percent of Consolidated Revenue			4.00%	5.00%
Rate decrease percent		22.00%	15.00%	22.00%	29.00%
Official exchange rate | $ / $		76.3	99.0	76.3	84.0		59.9
Net remeasurement loss			$ (6.6)	$ 5.3
Net monetary assets			58.6		$ 31.3
Cash and cash equivalents			49.1		24.4
Nonmonetary assets			143.2		146.2
Goodwill			99.8		99.8
Argentina conversion losses		$ 10.4
Devaluation settled rates		100.00%
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle	$ 413.3	$ 389.7	396.2	389.7	407.5		$ 457.4		$ 427.2		$ 455.2	$ 449.9
Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle					0.5	[1]	$ (1.7)	[2]
Accounting Standards Update 2016-13 | Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle													$ 1.7
Accounting Standards Update 2019-12 | Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle										$ 0.5
Internal Loss AR Rebuild
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Third-party expense				0.3
Increase (decrease) to bad debt expense			3.5	$ 9.6
Legal Fees			1.1
Provision for doubtful accounts			8.2
Accounts receivable			$ 8.2
Percent of Accounts Receivable			100.00%
Revolving Credit Facility
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted cash			$ 7.5		$ 5.0

[1] Effective January 1, 2021, we adopted the provisions of ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. We recognized a cumulative effect adjustment to January 1, 2021 retained earnings as a result of adopting this standard. See Note 1 for further details.

[2] Effective January 1, 2020, we adopted the provisions of ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. We recognized a cumulative effect adjustment to January 1, 2020 retained earnings as a result of adopting this standard. See Note 1 for further details.