Share-based compensation - Common Stock Granted to Nonemployee Directors (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Share-based compensation
Income tax benefit	$ 0.1	$ 0.3
Common stock
Share-based compensation
Shares granted (in shares)	0	1,509
Fair value	$ 0.0	$ 0.1
Income tax benefit	$ 0.0	$ 0.0

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