Income taxes - Tax Loss Carryforwards (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Income Tax Disclosure [Abstract]
U.S. Federal	$ 339.6
State and local	196.0
Foreign	252.0
Total tax loss carryforwards	787.6	$ 813.0
Operating Loss Carryforwards [Line Items]
Unlimited	277.3
Total tax loss carryforwards	787.6	$ 813.0
2025
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards, set to expire	20.4
2026
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards, set to expire	15.1
2027
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards, set to expire	19.0
2028
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards, set to expire	89.9
2029
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards, set to expire	4.9
Thereafter
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards, set to expire	$ 361.0

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-6

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible domestic operating loss carryforwards. Excludes state and local operating loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible state and local operating loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards that are subject to expiration dates.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-3

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