Condensed Consolidating Financial Information - Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Revenue:
Revenue	$ 259,293	$ 202,332	$ 514,868	$ 420,750
Cost of revenue:
Total cost of revenue	188,786	147,455	373,742	301,602
Gross profit	70,507	54,877	141,126	119,148
Operating expenses:
Selling, general and administrative	49,394	37,882	94,375	72,764
Amortization	6,438	4,815	12,736	9,381
Total operating expenses	55,832	42,697	107,111	82,145
Operating income (loss)	14,675	12,180	34,015	37,003
Other income (expense):
Net interest expense	(8,222)	(8,056)	(17,141)	(16,273)
Equity in earnings of subsidiaries			0
Other, net	1,973	(12)	2,127	(81)
Total other income (expense), net	(6,249)	(8,068)	(15,014)	(16,354)
Income from continuing operations before income taxes	8,426	4,112	19,001	20,649
Income tax benefit (provision)	(3,300)	(1,500)	(7,200)	(5,100)
Income from continuing operations	5,126	2,612	11,801	15,549
Income (loss) from discontinued operations, net of income taxes	6	(228)	159	(444)
Net income	5,132	2,384	11,960	15,105
Net income attributable to non-controlling interest	(591)	(283)	(752)	(579)
Net income attributable to Headwaters Incorporated	4,541	2,101	11,208	14,526
Building products
Revenue:
Revenue	140,716	98,101	275,757	199,696
Cost of revenue:
Total cost of revenue	99,782	69,639	196,311	139,191
Construction materials
Revenue:
Revenue	116,037	102,849	236,028	219,097
Cost of revenue:
Total cost of revenue	87,948	77,347	176,212	161,624
Energy technology
Revenue:
Revenue	2,540	1,382	3,083	1,957
Cost of revenue:
Total cost of revenue	1,056	469	1,219	787
Consolidation, Eliminations
Other income (expense):
Equity in earnings of subsidiaries	(15,928)	(11,021)	(33,493)	(29,647)
Total other income (expense), net	(15,928)	(11,021)	(33,493)	(29,647)
Income from continuing operations before income taxes	(15,928)	(11,021)	(33,493)	(29,647)
Income from continuing operations	(15,928)	(11,021)	(33,493)	(29,647)
Net income	(15,928)	(11,021)	(33,493)	(29,647)
Net income attributable to Headwaters Incorporated	(15,928)	(11,021)	(33,493)	(29,647)
Guarantor Subsidiaries
Revenue:
Revenue	244,728	189,919	485,341	396,137
Cost of revenue:
Total cost of revenue	178,408	138,763	351,613	284,345
Gross profit	66,320	51,156	133,728	111,792
Operating expenses:
Selling, general and administrative	37,053	29,331	71,065	57,025
Amortization	5,952	4,446	11,346	8,644
Total operating expenses	43,005	33,777	82,411	65,669
Operating income (loss)	23,315	17,379	51,317	46,123
Other income (expense):
Net interest expense	3	5	(121)	(95)
Other, net	94	(82)	20	(125)
Total other income (expense), net	97	(77)	(101)	(220)
Income from continuing operations before income taxes	23,412	17,302	51,216	45,903
Income tax benefit (provision)	(9,130)	(6,720)	(19,610)	(17,130)
Income from continuing operations	14,282	10,582	31,606	28,773
Net income	14,282	10,582	31,606	28,773
Net income attributable to Headwaters Incorporated	14,282	10,582	31,606	28,773
Guarantor Subsidiaries | Building products
Revenue:
Revenue	126,151	85,688	246,230	175,083
Cost of revenue:
Total cost of revenue	89,404	60,947	174,182	121,934
Guarantor Subsidiaries | Construction materials
Revenue:
Revenue	116,037	102,849	236,028	219,097
Cost of revenue:
Total cost of revenue	87,948	77,347	176,212	161,624
Guarantor Subsidiaries | Energy technology
Revenue:
Revenue	2,540	1,382	3,083	1,957
Cost of revenue:
Total cost of revenue	1,056	469	1,219	787
Non-Guarantor Subsidiaries
Revenue:
Revenue	14,565	12,413	29,527	24,613
Cost of revenue:
Total cost of revenue	10,378	8,692	22,129	17,257
Gross profit	4,187	3,721	7,398	7,356
Operating expenses:
Selling, general and administrative	1,927	1,859	4,051	3,553
Amortization	486	369	1,390	737
Total operating expenses	2,413	2,228	5,441	4,290
Operating income (loss)	1,774	1,493	1,957	3,066
Other income (expense):
Net interest expense	(2)	(3)	(4)	(3)
Other, net	1,879	70	2,107	44
Total other income (expense), net	1,877	67	2,103	41
Income from continuing operations before income taxes	3,651	1,560	4,060	3,107
Income tax benefit (provision)	(1,420)	(610)	(1,580)	(1,210)
Income from continuing operations	2,231	950	2,480	1,897
Income (loss) from discontinued operations, net of income taxes	6	(228)	159	(444)
Net income	2,237	722	2,639	1,453
Net income attributable to non-controlling interest	(591)	(283)	(752)	(579)
Net income attributable to Headwaters Incorporated	1,646	439	1,887	874
Non-Guarantor Subsidiaries | Building products
Revenue:
Revenue	14,565	12,413	29,527	24,613
Cost of revenue:
Total cost of revenue	10,378	8,692	22,129	17,257
Parent
Operating expenses:
Selling, general and administrative	10,414	6,692	19,259	12,186
Total operating expenses	10,414	6,692	19,259	12,186
Operating income (loss)	(10,414)	(6,692)	(19,259)	(12,186)
Other income (expense):
Net interest expense	(8,223)	(8,058)	(17,016)	(16,175)
Equity in earnings of subsidiaries	15,928	11,021	33,493	29,647
Total other income (expense), net	7,705	2,963	16,477	13,472
Income from continuing operations before income taxes	(2,709)	(3,729)	(2,782)	1,286
Income tax benefit (provision)	7,250	5,830	13,990	13,240
Income from continuing operations	4,541	2,101	11,208	14,526
Net income	4,541	2,101	11,208	14,526
Net income attributable to Headwaters Incorporated	$ 4,541	$ 2,101	$ 11,208	$ 14,526