Acquisitions (Details) $ in Thousands			3 Months Ended					9 Months Ended
	May. 16, 2014 USD ($)	Dec. 12, 2013 USD ($)	Jun. 30, 2015 USD ($) item	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Jun. 30, 2015 USD ($) item	Jun. 30, 2014 USD ($)
Acquisitions
Number of product categories in niche roofing | item			3					3
Estimated fair values of assets acquired and liabilities assumed
Goodwill			$ 175,512		$ 175,586			$ 175,512
Non-controlling interest in consolidated subsidiary
Balance				$ 13,252				13,252
Net income attributable to non-controlling interest			191			$ 389		695	$ 619
Balance			12,763		13,252			12,763
Entegra
Acquisitions
Total cash consideration of acquisition		$ 57,500
Fees for advisory, legal and other professional services					400
Estimated fair values of assets acquired and liabilities assumed
Current assets		8,261
Current liabilities		(3,422)
Property, plant and equipment		10,589
Goodwill		28,156
Net assets acquired		70,784
Less redeemable non-controlling interest		(13,252)
Net assets attributable to Headwaters		$ 57,532
Intangible assets acquired:
Noncontrolling equity interest (as a percent)		20.00%
Minimum period following the acquisition date after which remaining noncontrolling equity interest may be acquired		5 years
Period over which goodwill is expected to be deductible for tax purpose		15 years
Non-controlling interest in consolidated subsidiary
Balance				13,252				13,252
Net income attributable to non-controlling interest								695
Dividends paid to non-controlling interest								(1,184)
Balance			$ 12,763		13,252			$ 12,763
Entegra | Trade Names
Intangible assets acquired:
Indefinite lived intangible assets		$ 6,600
Entegra | Customer Relationships
Intangible assets acquired:
Finite lived intangible assets		$ 20,600
Estimated useful lives		15 years
Roof Tile Acquisition LLC
Intangible assets acquired:
Percentage of equity interests acquired		80.00%
Gerard
Acquisitions
Total cash consideration of acquisition	$ 27,600
Fees for advisory, legal and other professional services					300
Estimated fair values of assets acquired and liabilities assumed
Current assets	9,236
Current liabilities	(1,691)
Property, plant and equipment	8,314
Goodwill	7,719
Long-term liabilities	(3,906)
Net assets acquired	$ 27,572
Intangible assets acquired:
Period over which goodwill is expected to be deductible for tax purpose	15 years
Gerard | Trade Names
Intangible assets acquired:
Indefinite lived intangible assets	$ 3,900
Gerard | Customer Relationships
Intangible assets acquired:
Finite lived intangible assets	$ 4,000
Estimated useful lives	15 years
Other Business Acquisitions | Equity Method Investee
Acquisitions
Total cash consideration of acquisition				$ 1,200
Intangible assets acquired:
Percentage of equity interests acquired				100.00%
Construction materials | Other Business Acquisitions
Acquisitions
Total cash consideration of acquisition					$ 7,400		$ 3,100