Condensed Consolidating Financial Information - Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Revenue:
Revenue	$ 291,591	$ 262,466	$ 202,332	$ 218,418	$ 272,717	$ 243,294	$ 179,725	$ 199,597	$ 974,807	$ 895,333	$ 791,447
Cost of revenue:
Total cost of revenue									686,606	625,442	565,754
Gross profit	85,522	83,531	54,877	64,271	90,301	76,762	47,141	55,687	288,201	269,891	225,693
Operating expenses:
Selling, general and administrative									156,898	149,623	137,650
Amortization									20,593	18,161	21,319
Total operating expenses									177,491	167,784	158,969
Operating income									110,710	102,107	66,724
Other income (expense):
Net interest expense									(42,424)	(64,219)	(46,329)
Equity in earnings of subsidiaries									0	0	0
Other, net									4,149	(218)	(348)
Total other income (expense), net									(38,275)	(64,437)	(46,677)
Income from continuing operations before income taxes									72,435	37,670	20,047
Income tax benefit (provision)					96,800				(22,756)	94,458	(3,574)
Income from continuing operations									49,679	132,128	16,473
Income (loss) from discontinued operations, net of income taxes									84	(460)	(415)
Net income	$ 16,873	$ 17,785	$ 2,384	$ 12,721	$ 126,774	$ 23,008	$ (25,198)	$ 7,084	49,763	131,668	16,058
Net income attributable to non-controlling interest									(1,667)	(869)	(774)
Net income attributable to Headwaters Incorporated									48,096	130,799	15,284
Building products
Revenue:
Revenue									594,281	523,643	472,434
Cost of revenue:
Total cost of revenue									423,910	367,163	336,283
Construction materials
Revenue:
Revenue									370,439	352,263	309,337
Cost of revenue:
Total cost of revenue									258,478	249,077	224,888
Energy technology
Revenue:
Revenue									10,087	19,427	9,676
Cost of revenue:
Total cost of revenue									4,218	9,202	4,583
Consolidation, Eliminations
Other income (expense):
Equity in earnings of subsidiaries									(69,408)	(54,350)	(62,719)
Total other income (expense), net									(69,408)	(54,350)	(62,719)
Income from continuing operations before income taxes									(69,408)	(54,350)	(62,719)
Income from continuing operations									(69,408)	(54,350)	(62,719)
Net income									(69,408)	(54,350)	(62,719)
Net income attributable to Headwaters Incorporated									(69,408)	(54,350)	(62,719)
Guarantor Subsidiaries | Reportable Legal Entities
Revenue:
Revenue									918,736	851,028	757,486
Cost of revenue:
Total cost of revenue									644,694	593,795	541,691
Gross profit									274,042	257,233	215,795
Operating expenses:
Selling, general and administrative									119,702	115,423	108,602
Amortization									19,120	16,688	20,231
Total operating expenses									138,822	132,111	128,833
Operating income									135,220	125,122	86,962
Other income (expense):
Net interest expense									(306)	(205)	(349)
Intercompany interest income (expense)									(27,998)	(23,782)	(22,737)
Other, net									(434)	(56)	(24)
Total other income (expense), net									(28,738)	(24,043)	(23,110)
Income from continuing operations before income taxes									106,482	101,079	63,852
Income tax benefit (provision)									(41,371)	(48,213)	(3,296)
Income from continuing operations									65,111	52,866	60,556
Income (loss) from discontinued operations, net of income taxes										(67)	(415)
Net income									65,111	52,799	60,141
Net income attributable to Headwaters Incorporated									65,111	52,799	60,141
Guarantor Subsidiaries | Reportable Legal Entities | Building products
Revenue:
Revenue									538,210	479,338	438,473
Cost of revenue:
Total cost of revenue									381,998	335,516	312,220
Guarantor Subsidiaries | Reportable Legal Entities | Construction materials
Revenue:
Revenue									370,439	352,263	309,337
Cost of revenue:
Total cost of revenue									258,478	249,077	224,888
Guarantor Subsidiaries | Reportable Legal Entities | Energy technology
Revenue:
Revenue									10,087	19,427	9,676
Cost of revenue:
Total cost of revenue									4,218	9,202	4,583
Non-Guarantor Subsidiaries | Reportable Legal Entities
Revenue:
Revenue									56,071	44,305	33,961
Cost of revenue:
Total cost of revenue									41,912	31,647	24,063
Gross profit									14,159	12,658	9,898
Operating expenses:
Selling, general and administrative									8,956	6,174	4,209
Amortization									1,473	1,473	1,088
Total operating expenses									10,429	7,647	5,297
Operating income									3,730	5,011	4,601
Other income (expense):
Net interest expense									(35)		(2)
Intercompany interest income (expense)										(280)
Other, net									4,583	(162)	(324)
Total other income (expense), net									4,548	(442)	(326)
Income from continuing operations before income taxes									8,278	4,569	4,275
Income tax benefit (provision)									(2,398)	(1,756)	(923)
Income from continuing operations									5,880	2,813	3,352
Income (loss) from discontinued operations, net of income taxes									84	(393)
Net income									5,964	2,420	3,352
Net income attributable to non-controlling interest									(1,667)	(869)	(774)
Net income attributable to Headwaters Incorporated									4,297	1,551	2,578
Non-Guarantor Subsidiaries | Reportable Legal Entities | Building products
Revenue:
Revenue									56,071	44,305	33,961
Cost of revenue:
Total cost of revenue									41,912	31,647	24,063
Parent Company | Reportable Legal Entities
Operating expenses:
Selling, general and administrative									28,240	28,026	24,839
Total operating expenses									28,240	28,026	24,839
Operating income									(28,240)	(28,026)	(24,839)
Other income (expense):
Net interest expense									(42,083)	(64,014)	(45,978)
Intercompany interest income (expense)									27,998	24,062	22,737
Equity in earnings of subsidiaries									69,408	54,350	62,719
Total other income (expense), net									55,323	14,398	39,478
Income from continuing operations before income taxes									27,083	(13,628)	14,639
Income tax benefit (provision)									21,013	144,427	645
Income from continuing operations									48,096	130,799	15,284
Net income									48,096	130,799	15,284
Net income attributable to Headwaters Incorporated									$ 48,096	$ 130,799	$ 15,284