Income taxes - Differences between income tax expense (benefit) in Puerto Rico - subnote (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Mar. 31, 2024	Sep. 30, 2024
Reconciliation of Statutory Federal Tax Rate [Line Items]
Income tax credits and adjustments	$ 22.9	$ 22.9
Prior period correction adjustment
Reconciliation of Statutory Federal Tax Rate [Line Items]
Income tax credits and adjustments	$ 16.5	$ 16.5

A credit or adjustment for government or taxing authority authorized decrease in taxes owed as a result of meeting certain tax policy conditions.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-28

Name:	us-gaap_IncomeTaxCreditsAndAdjustments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration