Long-Term Borrowings - Additional Information (Details)				3 Months Ended								12 Months Ended
	May 01, 2017	Feb. 14, 2017 USD ($)	Mar. 03, 2016 USD ($)	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017 USD ($)	Jun. 24, 2017	Mar. 26, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 24, 2016 USD ($)		Sep. 26, 2015 USD ($)	Aug. 06, 2013 USD ($)	Aug. 02, 2013 USD ($)
Debt Instrument [Line Items]
Ownership interest in Suburban Energy Finance Corp (in hundredths)									100.00%			100.00%
Loss on debt extinguishment												$ 1,567,000	$ 292,000		$ 15,072,000
Long-term borrowings									$ 1,272,164,000			$ 1,272,164,000	$ 1,224,502,000	[1]
Consolidated interest coverage ratio, minimum												2.5
Total consolidated leverage ratio, maximum												5.5
Senior secured unconsolidated leverage ratio maximum												3.0
Notional Amount									100,000,000			$ 100,000,000
Consolidated fixed charge coverage ratio, minimum												1.75
Long-term debt maturities, 2018									0			$ 0
Long-term debt maturities, 2019									0			0
Long-term debt maturities, 2020									0			0
Long-term debt maturities, 2021									162,645,000			162,645,000
Long-term debt maturities, 2022									0			0
Long-term debt maturities, thereafter									1,125,000,000			1,125,000,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Standby letters of credit issued under the Revolving Credit Facility									$ 41,413,000			$ 41,413,000
Federal Funds Rate [Member]
Debt Instrument [Line Items]
Basis spread (in hundredths)												0.50%
Description of applicable interest rate on borrowings												Federal Funds Rate
LIBOR [Member]
Debt Instrument [Line Items]
Basis spread (in hundredths)												1.00%
Description of applicable interest rate on borrowings												LIBOR
Amended Credit Agreement Due 2021 [Member]
Debt Instrument [Line Items]
Weighted average interest rate (in hundredths)									3.80%			3.80%
Amended Credit Agreement Due 2021 [Member] | Federal Funds Rate [Member]
Debt Instrument [Line Items]
Basis spread (in hundredths)												0.50%
Description of applicable interest rate on borrowings												Federal Funds Rate
Amended Credit Agreement Due 2021 [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread (in hundredths)												1.00%
Description of applicable interest rate on borrowings												LIBOR
Amendment to Amended Credit Agreement Due 2021 [Member]
Debt Instrument [Line Items]
Total consolidated leverage ratio, maximum									5.95	5.95		5.5
Amendment to Amended Credit Agreement Due 2021 [Member] | Scenario, Forecast [Member]
Debt Instrument [Line Items]
Total consolidated leverage ratio, maximum				5.5	5.75	5.95	5.95	5.95
Amendment to Amended Credit Agreement Due 2021 [Member] | Eurodollar Rate Loans [Member]
Debt Instrument [Line Items]
Basis spread (in hundredths)	3.00%
Amendment to Amended Credit Agreement Due 2021 [Member] | Letter of Credit Fees [Member]
Debt Instrument [Line Items]
Basis spread (in hundredths)	3.00%
Amendment to Amended Credit Agreement Due 2021 [Member] | Base Rate Loans [Member]
Debt Instrument [Line Items]
Basis spread (in hundredths)	2.00%
Amendment to Amended Credit Agreement Due 2021 [Member] | Commitment Fee [Member]
Debt Instrument [Line Items]
Basis spread (in hundredths)	0.50%
Amended Credit Agreement Due 2017 [Member]
Debt Instrument [Line Items]
Effective date												Jun. 25, 2013
Termination date												Jan. 05, 2017
Fixed interest rate (in hundredths)									1.63%			1.63%
7.375% Senior Notes due August 1, 2021 [Member]
Debt Instrument [Line Items]
Date public offering completed												Aug. 01, 2012
Aggregate principal amount									$ 503,443,000			$ 503,443,000
Stated interest rate (in hundredths)									7.375%			7.375%	7.375%
Maturity date												Aug. 01, 2021
Debt instrument repurchase amount																$ 23,863,000	$ 133,400,000
Loss on debt extinguishment		$ 1,567,000
Redemption premium and related fees		15,078,000
Write-off unamortized debt origination costs		2,272,000										$ 1,567,000
Write-off unamortized premium		$ (15,783,000)
5.5% Senior Notes due June 1, 2024 [Member]
Debt Instrument [Line Items]
Date public offering completed												May 27, 2014
Aggregate principal amount									$ 525,000,000			$ 525,000,000
Stated interest rate (in hundredths)									5.50%			5.50%	5.50%
Maturity date												Jun. 01, 2024
Percentage of principal amount at which debt was issued (in hundredths)									100.00%			100.00%
Redemption start date												Jun. 01, 2019
Redemption description												The 2024 Senior Notes are redeemable, at the Partnership’s option, in whole or in part, at any time on or after June 1, 2019, in each case at the redemption prices, together with any accrued and unpaid interest to the date of the redemption.
Percentage of the principal amount repurchase offer under change of control provision (in hundredths)									101.00%			101.00%
Repurchase of debt due to decline in rating after consummation of change of control, period												90 days
7.5% Senior Notes due October 1, 2018 [Member]
Debt Instrument [Line Items]
Stated interest rate (in hundredths)									7.50%			7.50%
5.75% Senior Notes due March 1, 2025 [Member]
Debt Instrument [Line Items]
Date public offering completed												Feb. 25, 2015
Aggregate principal amount									$ 250,000,000			$ 250,000,000
Stated interest rate (in hundredths)									5.75%			5.75%	5.75%
Maturity date												Mar. 01, 2025
Percentage of principal amount at which debt was issued (in hundredths)									100.00%			100.00%
Redemption start date												Mar. 01, 2020
Redemption description												The 2025 Senior Notes are redeemable, at the Partnership’s option, in whole or in part, at any time on or after March 1, 2020, in each case at the redemption prices, together with any accrued and unpaid interest to the date of the redemption.
Percentage of the principal amount repurchase offer under change of control provision (in hundredths)									101.00%			101.00%
Repurchase of debt due to decline in rating after consummation of change of control, period												90 days
7.375% Senior Notes due March 15, 2020 [Member]
Debt Instrument [Line Items]
Stated interest rate (in hundredths)									7.375%			7.375%
Write-off unamortized debt origination costs															$ 2,855,000
5.875% Senior Notes due March 1, 2027 [Member]
Debt Instrument [Line Items]
Date public offering completed												Feb. 14, 2017
Aggregate principal amount									$ 350,000,000			$ 350,000,000
Stated interest rate (in hundredths)									5.875%			5.875%	5.875%
Maturity date												Mar. 01, 2027
Percentage of principal amount at which debt was issued (in hundredths)									100.00%			100.00%
Redemption start date												Mar. 01, 2022
Redemption description												The 2027 Senior Notes are redeemable, at the Partnership’s option, in whole or in part, at any time on or after March 1, 2022, in each case at the redemption prices, together with any accrued and unpaid interest to the date of the redemption.
Percentage of the principal amount repurchase offer under change of control provision (in hundredths)									101.00%			101.00%
Repurchase of debt due to decline in rating after consummation of change of control, period												90 days
Capitalized costs												$ 6,100,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Maturity date												Mar. 03, 2021
Long-term borrowings									$ 162,645,000			$ 162,645,000	$ 100,000,000
Revolving Credit Facility [Member] | Amended Credit Agreement Due 2021 [Member]
Debt Instrument [Line Items]
Write-off unamortized debt origination costs											$ 292,000		292,000
Revolving credit facility, term			5 years
Credit Facility, maximum amount			$ 500,000,000
Capitalized costs													2,678,000
Capitalized debt origination costs									$ 3,738,000			$ 3,738,000	$ 3,721,000

[1] Long-term borrowings as of September 24, 2016 reflect the retrospective impact from the adoption of new accounting guidance regarding the balance sheet classification of debt issuance costs (See Note 2).