Segment Reporting (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2016 USD ($) segment	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Segment Reporting
Number of business segments | segment									3
Segment revenue	$ 291,591	$ 262,466	$ 202,332	$ 218,418	$ 272,717	$ 243,294	$ 179,725	$ 199,597	$ 974,807	$ 895,333	$ 791,447
Depreciation and amortization									(62,518)	(53,973)	(55,134)
Operating income (loss)									110,710	102,107	66,724
Net interest expense									(42,424)	(64,219)	(46,329)
Other income (expense), net									4,149	(218)	(348)
Income tax benefit (provision)					96,800				(22,756)	94,458	(3,574)
Income from continuing operations									49,679	132,128	16,473
Income (loss) from discontinued operations, net of income taxes									84	(460)	(415)
Net income	16,873	$ 17,785	$ 2,384	$ 12,721	126,774	$ 23,008	$ (25,198)	$ 7,084	49,763	131,668	16,058
Capital expenditures									53,099	36,859	35,799
Segment assets	1,238,443				979,019				1,238,443	979,019	896,306
Building products
Segment Reporting
Segment revenue									594,281	523,643	472,434
Construction materials
Segment Reporting
Segment revenue									370,439	352,263	309,337
Energy technology
Segment Reporting
Segment revenue									10,087	19,427	9,676
Operating Segments | Building products
Segment Reporting
Segment revenue									594,281	523,643	472,434
Depreciation and amortization									(43,058)	(36,933)	(39,425)
Operating income (loss)									65,365	64,418	46,888
Capital expenditures									38,569	25,454	25,307
Segment assets	729,014				412,867				729,014	412,867	411,968
Operating Segments | Construction materials
Segment Reporting
Segment revenue									370,439	352,263	309,337
Depreciation and amortization									(16,717)	(15,155)	(13,706)
Operating income (loss)									76,099	64,984	51,503
Capital expenditures									7,159	5,855	5,721
Segment assets	332,593				294,057				332,593	294,057	325,140
Operating Segments | Energy technology
Segment Reporting
Segment revenue									10,087	19,427	9,676
Depreciation and amortization									(1,239)	(1,372)	(1,731)
Operating income (loss)									(2,514)	731	(6,829)
Capital expenditures									14	325	473
Segment assets	43,412				45,671				43,412	45,671	22,674
Corporate, Non-Segment
Segment Reporting
Segment revenue									0	0	0
Depreciation and amortization									(1,504)	(513)	(272)
Operating income (loss)									(28,240)	(28,026)	(24,838)
Capital expenditures									7,357	5,225	4,298
Segment assets	$ 133,424				$ 226,424				$ 133,424	$ 226,424	$ 136,524