Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014 segment	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting
Number of business segments									3
Segment reporting
Segment revenue	$ 245,921	$ 223,399	$ 156,512	$ 165,615	$ 214,985	$ 197,030	$ 140,988	$ 149,573	$ 791,447	$ 702,576	$ 632,787
Depreciation and amortization									(55,134)	(52,317)	(51,481)
Operating income (loss)									66,724	54,411	34,403
Net interest expense									(46,329)	(42,566)	(52,678)
Other income (expense), net									(348)	364	(7,493)
Income tax provision									(3,574)	(3,924)	(661)
Income (loss) from continuing operations									16,473	8,285	(26,429)
Loss from discontinued operations, net of income taxes									(415)	(1,148)	(35,819)
Net income (loss)	16,681	10,893	(10,082)	(1,434)	10,253	11,016	(8,260)	(5,872)	16,058	7,137	(62,248)
Capital expenditures									35,799	29,119	26,447
Segment assets	903,427				724,009				903,427	724,009	680,937
Operating Segments | Light Building Products
Segment reporting
Segment revenue									472,434	394,324	339,632
Depreciation and amortization									(39,425)	(37,065)	(35,724)
Operating income (loss)									46,888	34,194	25,553
Capital expenditures									25,307	21,455	17,707
Segment assets	411,968				306,686				411,968	306,686	271,554
Operating Segments | Heavy Construction Materials
Segment reporting
Segment revenue									309,337	293,000	281,672
Depreciation and amortization									13,706	(12,809)	(13,322)
Operating income (loss)									51,503	43,519	40,254
Capital expenditures									5,721	4,851	5,240
Segment assets	325,140				358,684				325,140	358,684	338,753
Operating Segments | Energy Technology
Segment reporting
Segment revenue									9,676	15,252	11,483
Depreciation and amortization									(1,731)	(2,153)	(2,287)
Operating income (loss)									(6,829)	(1,939)	(6,045)
Capital expenditures									473	634	1,472
Segment assets	22,674				34,509				22,674	34,509	36,377
Corporate, Non-Segment
Segment reporting
Segment revenue									0	0	0
Depreciation and amortization									(272)	(290)	(148)
Operating income (loss)									(24,838)	(21,363)	(25,359)
Capital expenditures									4,298	2,179	2,028
Segment assets	$ 143,645				$ 24,130				$ 143,645	$ 24,130	$ 34,253