Revenue Recognition (Disaggregated Net Sales) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) unit	Mar. 31, 2018 USD ($) unit
Disaggregation of Revenue [Line Items]
Net Sales	$ 113,822	$ 99,082
Rooftop Units
Disaggregation of Revenue [Line Items]
Net Sales	$ 88,343	$ 74,815
Total Units | unit	3,762,000	3,468,000
Condensing Units
Disaggregation of Revenue [Line Items]
Net Sales	$ 4,050	$ 4,281
Total Units | unit	394,000	411,000
Air Handlers
Disaggregation of Revenue [Line Items]
Net Sales	$ 5,594	$ 5,240
Total Units | unit	580,000	536,000
Outdoor Mechanical Rooms
Disaggregation of Revenue [Line Items]
Net Sales	$ 482	$ 973
Total Units | unit	11,000	14,000
Water Source Heat Pumps
Disaggregation of Revenue [Line Items]
Net Sales	$ 5,844	$ 4,387
Total Units | unit	2,289,000	1,614,000
Part Sales
Disaggregation of Revenue [Line Items]
Net Sales	$ 6,490	$ 5,960
Other
Disaggregation of Revenue [Line Items]
Net Sales	$ 3,019	$ 3,426
Total Units | unit	7,036,000	6,043,000