Segment Information - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Net Sales	$ 299,236	$ 280,086	$ 789,308	$ 761,459
Renewable Energy and Conservation
Disaggregation of Revenue [Line Items]
Net Sales	116,771	98,486	261,612	229,187
Residential Products
Disaggregation of Revenue [Line Items]
Net Sales	126,275	125,839	360,417	360,915
Industrial and Infrastructure Products
Disaggregation of Revenue [Line Items]
Net Sales	56,190	55,761	167,279	171,357
Point in Time
Disaggregation of Revenue [Line Items]
Net Sales	184,813	183,588	524,632	529,745
Point in Time | Renewable Energy and Conservation
Disaggregation of Revenue [Line Items]
Net Sales	12,682	10,784	28,441	25,128
Point in Time | Residential Products
Disaggregation of Revenue [Line Items]
Net Sales	125,350	125,118	357,808	358,960
Point in Time | Industrial and Infrastructure Products
Disaggregation of Revenue [Line Items]
Net Sales	46,781	47,686	138,383	145,657
Over Time
Disaggregation of Revenue [Line Items]
Net Sales	114,423	96,498	264,676	231,714
Over Time | Renewable Energy and Conservation
Disaggregation of Revenue [Line Items]
Net Sales	104,089	87,702	233,171	204,059
Over Time | Residential Products
Disaggregation of Revenue [Line Items]
Net Sales	925	721	2,609	1,955
Over Time | Industrial and Infrastructure Products
Disaggregation of Revenue [Line Items]
Net Sales	$ 9,409	$ 8,075	$ 28,896	$ 25,700