Revenue Recognition - Disaggregated Net Sales (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($) unit	Sep. 30, 2018 USD ($) unit	Sep. 30, 2019 USD ($) unit	Sep. 30, 2018 USD ($) unit
Disaggregation of Revenue [Line Items]
Net Sales	$ 113,500	$ 112,937	$ 346,759	$ 321,607
Rooftop Units
Disaggregation of Revenue [Line Items]
Net Sales	$ 78,432	$ 86,498	$ 255,532	$ 244,978
Total Units | unit	3,520,000	4,053,000	11,079,000	11,696,000
Condensing Units
Disaggregation of Revenue [Line Items]
Net Sales	$ 4,416	$ 5,356	$ 13,622	$ 14,492
Total Units | unit	418,000	611,000	1,291,000	1,647,000
Air Handlers
Disaggregation of Revenue [Line Items]
Net Sales	$ 6,523	$ 5,686	$ 18,150	$ 17,479
Total Units | unit	552,000	713,000	1,669,000	2,067,000
Outdoor Mechanical Rooms
Disaggregation of Revenue [Line Items]
Net Sales	$ 181	$ 311	$ 1,488	$ 2,178
Total Units | unit	7,000	8,000	28,000	35,000
Water Source Heat Pumps
Disaggregation of Revenue [Line Items]
Net Sales	$ 8,751	$ 3,112	$ 21,417	$ 10,240
Total Units | unit	1,311,000	1,162,000	5,977,000	3,780,000
Part Sales
Disaggregation of Revenue [Line Items]
Net Sales	$ 10,313	$ 5,030	$ 25,602	$ 17,692
Other
Disaggregation of Revenue [Line Items]
Net Sales	$ 4,884	$ 6,944	$ 10,948	$ 14,548
Total Units | unit	5,808,000	6,547,000	20,044,000	19,225,000