Revenue Recognition - Disaggregated Net Sales (Details) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020 USD ($) unit	Sep. 30, 2019 USD ($) unit	Sep. 30, 2020 USD ($) unit	Sep. 30, 2019 USD ($) unit
Disaggregation of Revenue [Line Items]
Net Sales	$ 134,772	$ 113,500	$ 397,851	$ 346,759
Rooftop units
Disaggregation of Revenue [Line Items]
Net Sales	$ 102,750	$ 78,432	$ 312,725	$ 255,532
Total Units \| unit	4,372,000	3,520,000	12,179,000	11,079,000
Condensing units
Disaggregation of Revenue [Line Items]
Net Sales	$ 6,304	$ 4,416	$ 15,307	$ 13,622
Total Units \| unit	593,000	418,000	1,447,000	1,291,000
Air handlers
Disaggregation of Revenue [Line Items]
Net Sales	$ 5,805	$ 6,523	$ 18,068	$ 18,150
Total Units \| unit	534,000	552,000	1,545,000	1,669,000
Outdoor mechanical rooms
Disaggregation of Revenue [Line Items]
Net Sales	$ 867	$ 181	$ 2,216	$ 1,488
Total Units \| unit	6,000	7,000	22,000	28,000
Water source heat pumps
Disaggregation of Revenue [Line Items]
Net Sales	$ 6,770	$ 8,751	$ 14,269	$ 21,417
Total Units \| unit	1,847,000	1,311,000	5,109,000	5,977,000
Part sales
Disaggregation of Revenue [Line Items]
Net Sales	$ 10,484	$ 10,313	$ 24,562	$ 25,602
Other
Disaggregation of Revenue [Line Items]
Net Sales	$ 1,792	$ 4,884	$ 10,704	$ 10,948
Total Units \| unit	7,352,000	5,808,000	20,302,000	20,044,000