Accounts receivable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Receivables [Abstract]
Revenue recognized in excess of billings on services contracts or unbilled accounts receivable	$ 87.9	$ 73.1
Unearned income	13.9	4.1
Allowance for doubtful accounts	9.1	8.0
Provision for doubtful accounts reported in selling, general and administrative expenses, (income) expense	0.3	(0.6)	$ (0.3)
Long-term receivables	$ 85.3	$ 49.1