Selected Quarterly Financial Data (Detail) (USD $) In Thousands, except Per Share data, 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		Sep. 30, 2013		Sep. 30, 2012
Selected Quarterly Financial Data [Line Items]
Sales	$ 222,362		$ 326,511		$ 892,241		$ 520,610		$ 177,608		$ 262,524		$ 785,139		$ 516,525		$ 1,961,724		$ 1,741,796		$ 1,497,588
Gross profit for product, installation and service	37,507		60,682		199,645		108,590		33,519		54,907		162,011		102,691		406,424		353,128
Operating income (loss)	(40,188)		(10,797)		93,953		36,887		(19,800)		(8,001)		75,229		18,577		79,855		66,005		58,259
Income (loss) before income taxes	(44,115)		(16,618)		89,289		32,843		(23,686)		(11,952)		70,796		14,669		61,399		49,827		42,565
Net income (loss)	(25,828)		(9,592)		52,216		19,288		(13,937)		(7,588)		41,679		9,752		36,084		29,906		25,989
Limited Partner interest in net income (loss)	$ (25,682)		$ (9,538)		$ 51,922		$ 19,179		$ (13,859)		$ (7,547)		$ 41,454		$ 9,699		$ 35,881		$ 29,747		$ 25,853
Net income (loss) per Limited Partner unit:
Basic and diluted	$ (0.45)	[1]	$ (0.17)	[1]	$ 0.75	[1]	$ 0.29	[1]	$ (0.24)	[1]	$ (0.13)	[1]	$ 0.58	[1]	$ 0.15	[1]	$ 0.57	[1],[2]	$ 0.47	[1],[2]	$ 0.40	[2]

[1] The sum of the quarters do not add-up to the total due to the weighting of Limited Partner Units outstanding, rounding or the theoretical effects of FASB ASC 260-10-45-60 to Master Limited Partners earnings per unit.

[2] See Note 17 Earnings Per Limited Partner Units.