Reportable Business Segments (Assets by Segment) (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Segment Reporting Information [Line Items]
Total assets	$ 4,689.3	$ 4,081.8
Operating Segments
Segment Reporting Information [Line Items]
Total assets	4,279.9	3,717.4
Corporate and Other
Segment Reporting Information [Line Items]
Total assets	409.4	364.4
Residential Heating and Cooling [Member] \| Operating Segments
Segment Reporting Information [Line Items]
Total assets	2,375.2	1,971.0
Commercial Heating and Cooling \| Operating Segments
Segment Reporting Information [Line Items]
Total assets	$ 1,904.7	$ 1,746.4

Amount of asset recognized for present right to economic benefit.

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+ Details