Segment Information - Disclosure by Reportable Segment and Reconciliation of Total Operating Segment Information (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Mar. 31, 2018	Mar. 25, 2017	Mar. 31, 2018	Mar. 25, 2017	Sep. 30, 2017
Revenues [Abstract]
Total revenues		$ 536,282	$ 450,578	$ 909,559	$ 767,885
Operating income (loss):
Total operating income		126,230	102,857	181,978	156,342
Reconciliation to net income:
Loss on debt extinguishment		0	1,567	0	1,567
Interest expense, net		19,402	17,487	38,916	36,318
Provision for (benefit from) income taxes		41	(9)	(893)	156
Net income		106,787	83,812	143,955	118,301
Depreciation and amortization [Abstract]
Total depreciation and amortization		32,203	32,670	63,334	63,931
Assets [Abstract]
Total assets		2,227,981		2,227,981		$ 2,171,283
Operating/Reportable Segments [Member] | Propane [Member]
Revenues [Abstract]
Total revenues		462,814	385,654	784,944	655,113
Operating income (loss):
Total operating income	[1]	143,221	115,346	217,772	190,009
Depreciation and amortization [Abstract]
Total depreciation and amortization		28,288	28,072	56,069	55,456
Assets [Abstract]
Total assets		2,093,843		2,093,843		2,066,997
Operating/Reportable Segments [Member] | Fuel Oil and Refined Fuels [Member]
Revenues [Abstract]
Total revenues		41,699	34,630	67,014	56,726
Operating income (loss):
Total operating income		7,199	6,828	11,023	9,676
Depreciation and amortization [Abstract]
Total depreciation and amortization		716	667	1,295	1,298
Assets [Abstract]
Total assets		58,291		58,291		49,863
Operating/Reportable Segments [Member] | Natural Gas and Electricity [Member]
Revenues [Abstract]
Total revenues		20,392	19,239	33,539	32,306
Operating income (loss):
Total operating income		5,454	5,535	8,939	8,655
Depreciation and amortization [Abstract]
Total depreciation and amortization		0	0	0	0
Assets [Abstract]
Total assets		17,053		17,053		12,455
Operating/Reportable Segments [Member] | All Other [Member]
Revenues [Abstract]
Total revenues		11,377	11,055	24,062	23,740
Operating income (loss):
Total operating income		(4,981)	(5,186)	(10,214)	(10,392)
Depreciation and amortization [Abstract]
Total depreciation and amortization		56	76	106	146
Assets [Abstract]
Total assets		3,228		3,228		2,147
Operating/Reportable Segments [Member] | Corporate [Member]
Operating income (loss):
Total operating income		(24,663)	(19,666)	(45,542)	(41,606)
Depreciation and amortization [Abstract]
Total depreciation and amortization		3,143	$ 3,855	5,864	$ 7,031
Assets [Abstract]
Total assets		$ 55,566		$ 55,566		$ 39,821

[1] Includes the loss on sale of business of $4,823 for the six months ended March 31, 2018 (see Note 3).