Revenue Recognition (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Contract with Customer, Liability, Revenue Recognized	$ 1,600,000	$ 1,500,000
Residential Heating and Cooling [Member] | Sales Channel, Directly to Consumer [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0.67	0.73
Commercial Heating and Cooling [Member] | Equipment Sales [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 0.83	$ 0.84