Share-based compensation - Schedule of Common Stock Granted to Nonemployee Directors (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Share-based compensation
Income tax benefit	$ 0.5	$ 0.5	$ 0.6	$ 0.5
Common stock
Share-based compensation
Shares granted (in shares)	92,380	117,590	92,380	117,590
Fair value	$ 1.2	$ 1.2	$ 1.2	$ 1.2
Income tax benefit	$ 0.3	$ 0.3	$ 0.3	$ 0.3

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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+ Details