Acquisitions (Details) $ in Thousands			1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 17, 2016 USD ($)	Dec. 03, 2015 USD ($)	Dec. 03, 2015 USD ($) item	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Nov. 13, 2015	Sep. 30, 2015 USD ($)	Sep. 30, 2014
Acquisitions
Consideration paid net of cash acquired						$ 96,457	$ 1,200
Estimated fair values of assets acquired and liabilities assumed
Goodwill				$ 246,167		246,167			$ 178,199
Intangible assets acquired:
Revenue				202,332	$ 179,725	420,750	379,322
Net income (loss)				2,384	(25,198)	15,105	(18,114)
Pro forma consolidated revenue and net income (loss)
Pro forma revenue				207,224	190,466	435,713	402,340
Pro forma net income (loss)				3,337	(24,272)	17,247	(16,569)
Non-controlling interest in consolidated subsidiary
Balance						12,431
Net income attributable to non-controlling interest				283	259	579	504
Dividends paid to non-controlling interest						(735)
Balance				12,275		12,275
Entegra
Acquisitions
Percentage of equity interests acquired										80.00%
Pro forma consolidated revenue and net income (loss)
Noncontrolling equity interest (as a percent)										20.00%
Acquisitions 2016
Intangible assets acquired:
Revenue				3,400	0	5,400	0
Net income (loss)				(1,000)	$ 0	(1,400)	$ 0
Acquisitions 2016 | Acquisition-related Costs
Pro forma consolidated revenue and net income (loss)
Fees for advisory, legal and other professional services				500		500
Acquisitions 2016 | Fair Value Adjustment to Inventory
Pro forma consolidated revenue and net income (loss)
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		$ 7,610	7,610
Current liabilities		(1,059)	(1,059)
Property, plant and equipment		1,411	1,411
Goodwill		25,627	25,627
Net assets acquired		56,995	$ 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	$ 5,566
Roofing Businesses | Intellectual property
Intangible assets acquired:
Indefinite lived intangible assets		9,800	9,800
Roofing Businesses | Customer Relationships
Intangible assets acquired:
Finite lived intangible assets		$ 8,040	$ 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	$ 33,100
Future estimated consideration payments accrued	12,000
Estimated fair values of assets acquired and liabilities assumed
Current assets	4,210
Current liabilities	(2,588)
Property, plant and equipment	3,258
Goodwill and intangible assets	40,243
Net assets acquired	$ 45,123
Intangible assets acquired:
Period over which goodwill is expected to be deductible for tax purpose	15 years
Other Business Acquisitions
Acquisitions
Total cash consideration of acquisition				$ 6,300