Acquisitions (Details) $ in Thousands		1 Months Ended		3 Months Ended			9 Months Ended
	Mar. 17, 2016 USD ($)	Aug. 03, 2016 USD ($)	Dec. 03, 2015 USD ($) item	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Nov. 13, 2015	Sep. 30, 2015 USD ($)	Sep. 30, 2014
Acquisitions
Consideration paid net of cash acquired							$ 106,924	$ 1,200
Estimated fair values of assets acquired and liabilities assumed
Goodwill				$ 218,722			218,722			$ 178,199
Intangible assets acquired:
Revenue				262,466		$ 243,294	683,216	622,616
Net income (loss)				17,785		23,008	32,890	4,894
Pro forma consolidated revenue and net income
Pro forma revenue				262,766		262,730	702,300	669,483
Pro forma net income				17,830		26,179	33,579	8,461
Non-controlling interest in consolidated subsidiary
Balance		$ 12,544					12,431
Net income attributable to non-controlling interest				269		191	848	695
Dividends paid to non-controlling interest							(735)
Balance				12,544			12,544
Entegra
Acquisitions
Percentage of equity interests acquired											80.00%
Pro forma consolidated revenue and net income
Noncontrolling equity interest (as a percent)											20.00%
Acquisitions 2016
Intangible assets acquired:
Revenue				15,600		0	22,200	0
Net income (loss)				900		$ 0	(400)	$ 0
Acquisitions 2016 | Acquisition-related Costs
Pro forma consolidated revenue and net income
Fees for advisory, legal and other professional services				500			500
Acquisitions 2016 | Fair Value Adjustment to Inventory
Pro forma consolidated revenue and net income
Nonrecurring expense related to the fair value adjustment to acquisition-date inventory				500			$ 500
Roofing Businesses
Acquisitions
Number of acquisitions aggregated | item			2
Consideration paid net of cash acquired			$ 57,000
Estimated fair values of assets acquired and liabilities assumed
Current assets			7,401
Current liabilities			(1,326)
Property, plant and equipment			1,411
Goodwill			26,103
Net assets acquired			$ 56,995
Intangible assets acquired:
Period over which goodwill is expected to be deductible for tax purpose			15 years
Roofing Businesses | Trade names
Intangible assets acquired:
Indefinite lived intangible assets			$ 5,566
Roofing Businesses | Intellectual property
Intangible assets acquired:
Indefinite lived intangible assets			9,800
Roofing Businesses | Customer relationships
Intangible assets acquired:
Finite lived intangible assets			$ 8,040
Estimated useful lives of the identified intangible assets			12 years
Metro Roof Products
Acquisitions
Percentage of equity interests acquired									100.00%
SynMat
Acquisitions
Percentage of equity interests acquired	100.00%
Consideration paid net of cash acquired	$ 33,200
Future estimated consideration payments accrued	12,000
Estimated fair values of assets acquired and liabilities assumed
Current assets	4,210
Current liabilities	(1,453)
Property, plant and equipment	3,258
Goodwill	13,249
Net assets acquired	$ 45,164
Intangible assets acquired:
Period over which goodwill is expected to be deductible for tax purpose	15 years
SynMat | Trade names
Intangible assets acquired:
Indefinite lived intangible assets	$ 5,650
SynMat | Contracts
Intangible assets acquired:
Finite lived intangible assets	$ 17,370
Estimated useful lives of the identified intangible assets	20 years
SynMat | Customer relationships
Intangible assets acquired:
Finite lived intangible assets	$ 2,880
Estimated useful lives of the identified intangible assets	15 years
Decking Manufacturing Assets
Acquisitions
Total cash consideration of acquisition					$ 6,300
Concrete Roof Tile Business
Acquisitions
Total cash consideration of acquisition				$ 10,400
Krestmark Industries
Acquisitions
Total cash consideration of acquisition		$ 240,000