Segment Information (Measurements Used by Management to Assess Performance of Segments) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales	$ 231,838	$ 272,734	$ 265,738	$ 237,671	$ 282,093	$ 304,994	$ 253,171	$ 200,615	$ 1,007,981	$ 1,040,873	$ 862,087
Income (loss) from operations:	584	$ 26,363	$ 28,416	$ 17,601	4,520	$ 23,394	$ 11,201	$ 8,970	72,964	48,085	(70,417)
Depreciation and amortization									24,114	30,548	25,432
Total assets	918,245				889,772				918,245	889,772	810,471
Capital expenditures									10,779	12,373	23,291
Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Income (loss) from operations:									43,214	12,659	0
Intersegment sales
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales:									(1,495)	(1,536)	(1,260)
Unallocated Corporate Expenses
Segment Reporting, Other Significant Reconciling Item [Line Items]
Income (loss) from operations:									(36,797)	(26,959)	(12,199)
Depreciation and amortization									377	662	823
Total assets	153,338				37,235				153,338	37,235	108,229
Capital expenditures									377	328	135
Residential Products | Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales									430,938	475,653	431,915
Income (loss) from operations:									65,241	46,804	16,416
Depreciation and amortization									9,297	9,967	10,699
Total assets	331,975				363,339				331,975	363,339	394,092
Capital expenditures									5,182	3,328	12,731
Industrial and Infrastructure Products
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales									295,018	376,688	430,172
Industrial and Infrastructure Products | Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales:									296,513	378,224	431,432
Income (loss) from operations:									1,306	15,581	(74,634)
Depreciation and amortization									8,237	12,108	13,910
Total assets	225,691				273,987				225,691	273,987	308,150
Capital expenditures									2,060	4,846	10,425
Renewable Energy & Conservation | Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net sales									282,025	188,532	0
Depreciation and amortization									6,203	7,811	0
Total assets	$ 207,241				$ 215,211				207,241	215,211	0
Capital expenditures									$ 3,160	$ 3,871	$ 0