Marketable securities - Schedule of Marketable Securities (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2025	Dec. 31, 2024
Marketable securities [Line Items]
Market value, current	$ 2.4	$ 1.9
Market value, noncurrent	4.7	5.7
Noncurrent assets
Marketable securities [Line Items]
Unrealized gain, net	0.2
Current assets
Marketable securities [Line Items]
Market value, current	2.4	1.9
Cost or amortized cost	2.4	1.9
Noncurrent assets
Marketable securities [Line Items]
Market value, noncurrent	4.7	5.7
Cost or amortized cost	$ 4.5	$ 5.7

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

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Amount of investment in marketable security, classified as current.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
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Amount of investment in marketable security, classified as noncurrent.

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Amount of unrealized gain (loss) on investment in marketable security.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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