Goodwill (Details) - USD ($) $ in Millions		12 Months Ended
	Oct. 15, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Goodwill
Beginning Balance		$ 220.0	$ 222.1
Goodwill, adjustment		(2.1)	(2.1)
Goodwill from business acquisition	$ 277.2	277.2
Ending Balance		497.2	220.0
Goodwill, accumulated impairment losses				$ 37.3
AES
Goodwill
Beginning Balance		38.3	40.4
Goodwill, adjustment			(2.1)
Ending Balance			38.3
Segment Reporting, Reconciling Item, Corporate Nonsegment
Goodwill
Beginning Balance		0.0	0.0
Goodwill, adjustment			0.0
Goodwill from business acquisition		0.0
Ending Balance		0.0	0.0
Residential Heating & Cooling [Member] | Operating Segments
Goodwill
Beginning Balance		26.1	26.1
Goodwill, adjustment			0.0
Goodwill from business acquisition		60.9
Ending Balance		87.0	26.1
Commercial Heating & Cooling [Member] | Operating Segments
Goodwill
Beginning Balance		193.9	196.0
Goodwill, adjustment			(2.1)
Goodwill from business acquisition	$ 216.3	216.3
Ending Balance		$ 410.2	$ 193.9