Revenue Recognition (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Contract with Customer, Liability, Revenue Recognized	$ 600,000	$ 1,400,000	$ 2,900,000	$ 5,900,000
Residential Heating and Cooling [Member] | Sales Channel, Directly to Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0.73	0.74	0.72	0.75
Commercial Heating and Cooling [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 0.81	$ 0.83	$ 0.83	$ 0.84