Condensed Consolidating Financial Information (Details 3) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Revenue:
Revenue	$ 272,717	$ 243,294	$ 179,725	$ 199,597	$ 245,921	$ 223,399	$ 156,512	$ 165,615	$ 895,333	$ 791,447	$ 702,576
Cost of revenue:
Total cost of revenue									625,442	565,754	510,094
Gross profit	90,301	76,762	47,141	55,687	78,577	67,672	38,551	40,893	269,891	225,693	192,482
Operating expenses:
Selling, general and administrative									149,623	137,650	117,841
Amortization									18,161	21,319	20,230
Total operating expenses									167,784	158,969	138,071
Operating income									102,107	66,724	54,411
Other income (expense):
Net interest expense									(64,219)	(46,329)	(42,566)
Equity in earnings of subsidiaries									0	0	0
Other, net									(218)	(348)	364
Total other income (expense), net									(64,437)	(46,677)	(42,202)
Income from continuing operations before income taxes									37,670	20,047	12,209
Income tax benefit (provision)	(96,800)								94,458	(3,574)	(3,924)
Income from continuing operations									132,128	16,473	8,285
Loss from discontinued operations, net of income taxes									(460)	(415)	(1,148)
Net income	$ 126,774	$ 23,008	$ (25,198)	$ 7,084	$ 16,681	$ 10,893	$ (10,082)	$ (1,434)	131,668	16,058	7,137
Net income attributable to non-controlling interest									(869)	(774)	0
Net income attributable to Headwaters Incorporated									130,799	15,284	7,137
Building products
Revenue:
Revenue									523,643	472,434	394,324
Cost of revenue:
Total cost of revenue									367,163	336,283	283,128
Construction materials
Revenue:
Revenue									352,263	309,337	293,000
Cost of revenue:
Total cost of revenue									249,077	224,888	219,996
Energy Technology
Revenue:
Revenue									19,427	9,676	15,252
Cost of revenue:
Total cost of revenue									9,202	4,583	6,970
Consolidation, Eliminations
Other income (expense):
Equity in earnings of subsidiaries									(54,350)	(62,719)	(47,117)
Total other income (expense), net									(54,350)	(62,719)	(47,117)
Income from continuing operations before income taxes									(54,350)	(62,719)	(47,117)
Income from continuing operations									(54,350)	(62,719)	(47,117)
Net income									(54,350)	(62,719)	(47,117)
Net income attributable to Headwaters Incorporated									(54,350)	(62,719)
Guarantor Subsidiaries | Reportable Legal Entities
Revenue:
Revenue									851,028	757,486	702,576
Cost of revenue:
Total cost of revenue									593,795	541,691	510,094
Gross profit									257,233	215,795	192,482
Operating expenses:
Selling, general and administrative									115,423	108,602	96,478
Amortization									16,688	20,231	20,230
Total operating expenses									132,111	128,833	116,708
Operating income									125,122	86,962	75,774
Other income (expense):
Net interest expense									(205)	(349)	(54)
Intercompany interest income (expense)									(23,782)	(22,737)	(23,434)
Other, net									(56)	(24)	329
Total other income (expense), net									(24,043)	(23,110)	(23,159)
Income from continuing operations before income taxes									101,079	63,852	52,615
Income tax benefit (provision)									(48,213)	(3,296)	(4,350)
Income from continuing operations									52,866	60,556	48,265
Loss from discontinued operations, net of income taxes									(67)	(415)	(1,148)
Net income									52,799	60,141	47,117
Net income attributable to Headwaters Incorporated									52,799	60,141
Guarantor Subsidiaries | Reportable Legal Entities | Building products
Revenue:
Revenue									479,338	438,473	394,324
Cost of revenue:
Total cost of revenue									335,516	312,220	283,128
Guarantor Subsidiaries | Reportable Legal Entities | Construction materials
Revenue:
Revenue									352,263	309,337	293,000
Cost of revenue:
Total cost of revenue									249,077	224,888	219,996
Guarantor Subsidiaries | Reportable Legal Entities | Energy Technology
Revenue:
Revenue									19,427	9,676	15,252
Cost of revenue:
Total cost of revenue									9,202	4,583	6,970
Non-Guarantor Subsidiaries | Reportable Legal Entities
Revenue:
Revenue									44,305	33,961
Cost of revenue:
Total cost of revenue									31,647	24,063
Gross profit									12,658	9,898
Operating expenses:
Selling, general and administrative									6,174	4,209
Amortization									1,473	1,088
Total operating expenses									7,647	5,297
Operating income									5,011	4,601
Other income (expense):
Net interest expense										(2)
Intercompany interest income (expense)									(280)
Other, net									(162)	(324)
Total other income (expense), net									(442)	(326)
Income from continuing operations before income taxes									4,569	4,275
Income tax benefit (provision)									(1,756)	(923)
Income from continuing operations									2,813	3,352
Loss from discontinued operations, net of income taxes									(393)
Net income									2,420	3,352
Net income attributable to non-controlling interest									(869)	(774)
Net income attributable to Headwaters Incorporated									1,551	2,578
Non-Guarantor Subsidiaries | Reportable Legal Entities | Building products
Revenue:
Revenue									44,305	33,961
Cost of revenue:
Total cost of revenue									31,647	24,063
Parent Company | Reportable Legal Entities
Operating expenses:
Selling, general and administrative									28,026	24,839	21,363
Total operating expenses									28,026	24,839	21,363
Operating income									(28,026)	(24,839)	(21,363)
Other income (expense):
Net interest expense									(64,014)	(45,978)	(42,512)
Intercompany interest income (expense)									24,062	22,737	23,434
Equity in earnings of subsidiaries									54,350	62,719	47,117
Other, net											35
Total other income (expense), net									14,398	39,478	28,074
Income from continuing operations before income taxes									(13,628)	14,639	6,711
Income tax benefit (provision)									144,427	645	426
Income from continuing operations									130,799	15,284	7,137
Net income									130,799	15,284	$ 7,137
Net income attributable to Headwaters Incorporated									$ 130,799	$ 15,284