Earnings Per Share - Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Numerator:
Income from continuing operations									$ 49,679	$ 132,128	$ 16,473
Income from continuing operations attributable to non-controlling interest									(1,667)	(869)	(774)
Adjustment of estimated redemption value of non-controlling interest in consolidated subsidiary											(176)
Numerator for basic and diluted earnings per share from continuing operations — income from continuing operations attributable to Headwaters Incorporated									48,012	131,259	15,523
Numerator for basic and diluted earnings per share from discontinued operations - income (loss) from discontinued operations, net of income taxes									84	(460)	(415)
Numerator for basic and diluted earnings per share — net income attributable to Headwaters Incorporated									$ 48,096	$ 130,799	$ 15,108
Denominator:
Denominator for basic earnings per share - weighted-average shares outstanding									73,842	73,570	73,160
Effect of dilutive securities - shares issuable upon exercise of options and SARs and vesting of restricted stock									1,573	2,032	1,291
Denominator for diluted earnings per share - weighted-average shares outstanding after assumed exercises and vesting									75,415	75,602	74,451
Basic income per share attributable to Headwaters Incorporated:
From continuing operations (in dollars per share)									$ 0.65	$ 1.79	$ 0.21
From discontinued operations (in dollars per share)									0.00	(0.01)	(0.01)
Basic income per share (in dollars per share)	$ 0.21	$ 0.23	$ 0.03	$ 0.17	$ 1.72	$ 0.30	$ (0.34)	$ 0.09	0.65	1.78	0.20
Diluted income per share attributable to Headwaters Incorporated:
From continuing operations (in dollars per share)									0.64	1.74	0.21
From discontinued operations (in dollars per share)									0.00	(0.01)	(0.01)
Diluted income per share (in dollars per share)	$ 0.21	$ 0.23	$ 0.03	$ 0.17	$ 1.68	$ 0.30	$ (0.34)	$ 0.09	$ 0.64	$ 1.73	$ 0.20