Reportable Business Segments (Assets by Segment) (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Segment Reporting Information [Line Items]
Total assets	$ 4,292.7	$ 4,081.8
Operating Segments
Segment Reporting Information [Line Items]
Total assets	3,873.9	3,717.4
Corporate and Other
Segment Reporting Information [Line Items]
Total assets	418.8	364.4
Residential Heating and Cooling [Member] | Operating Segments
Segment Reporting Information [Line Items]
Total assets	2,078.1	1,971.0
Commercial Heating and Cooling | Operating Segments
Segment Reporting Information [Line Items]
Total assets	$ 1,795.8	$ 1,746.4