Restrictions on cash and investments (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Investments In Debt And Equity Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Investments restricted for statutory reserve funds	$ 527.4	$ 544.0
Cash and Cash Equivalents
Restricted Cash and Cash Equivalents Items [Line Items]
Investments restricted for statutory reserve funds	$ 10.0	$ 8.6

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.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1

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