Long-Term Borrowings - Additional Information (Details) $ in Thousands		12 Months Ended
	Dec. 28, 2022 USD ($)	Sep. 27, 2025 USD ($)	Sep. 28, 2024 USD ($)	Sep. 30, 2023 USD ($)	Mar. 15, 2024 USD ($)
Debt Instrument [Line Items]
Ownership interest in Suburban Energy Finance Corp (in hundredths)		100.00%
Stated interest rate (in hundredths)	5.50%
Long-term borrowings	$ 80,645	$ 1,218,892	$ 1,219,167
SPH Debt Service Coverage Ratio Minimum	0.01
Loss on debt extinguishment		$ 0	215	$ 0
Consolidated fixed charge coverage ratio, minimum		1.75
Capitalized costs		$ 3,744
Long-term debt maturities, 2026		0
Long-term debt maturities, 2027		499,200
Long-term debt maturities, 2028		0
Long-term debt maturities, 2029		11,707
Long-term debt maturities, 2030		12,352
Long-term debt maturities, thereafter		$ 706,586
Federal Funds Rate [Member]
Debt Instrument [Line Items]
Description of applicable interest rate on borrowings		Federal Funds Rate
Margin over basis rate (in hundredths)		0.50%
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Description of applicable interest rate on borrowings		SOFR
Margin over basis rate (in hundredths)		1.00%
Fourth Amended And Restated Credit Agreement [Member]
Debt Instrument [Line Items]
Deferred debt issuance cost, writeoff			215
Amended Revolving Credit Facility Due2025 [Member]
Debt Instrument [Line Items]
Margin over basis rate (in hundredths)		1.00%
Weighted average interest rate (in hundredths)		6.84%
Amended Revolving Credit Facility Due2025 [Member] | Federal Funds Rate [Member]
Debt Instrument [Line Items]
Description of applicable interest rate on borrowings		Federal Funds Rate
Margin over basis rate (in hundredths)		0.50%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term borrowings		$ 149,200	151,000
Maturity date		Mar. 15, 2029
Deferred debt issuance cost, writeoff		$ 215
Consolidated interest coverage ratio, minimum		2.5
Total consolidated leverage ratio		5.75
Senior secured unconsolidated leverage ratio maximum		3.25
Standby letters of credit issued under the Revolving Credit Facility		$ 26,386
Standby letters of credit issued under the Revolving Credit Facility, expiration date		Apr. 30, 2026
Revolving Credit Facility [Member] | Third Amended and Restated Credit [Member]
Debt Instrument [Line Items]
Long-term borrowings		$ 187,900
Revolving Credit Facility [Member] | Fourth Amended And Restated Credit Agreement [Member]
Debt Instrument [Line Items]
Long-term borrowings		$ 149,200	151,000
Maturity date		Mar. 15, 2029
Credit Facility, maximum amount					$ 500,000
Capitalized debt origination costs		$ 1,743	$ 3,237
5.875% Senior Notes due March 1, 2027 [Member]
Debt Instrument [Line Items]
Stated interest rate (in hundredths)		5.875%	5.875%
Maturity date		Mar. 01, 2027	Mar. 01, 2027
5.0% Senior Notes due June 1, 2031 [Member]
Debt Instrument [Line Items]
Ownership interest in Suburban Energy Finance Corp (in hundredths)		100.00%
Stated interest rate (in hundredths)		5.00%	5.00%
Date public offering completed		May 24, 2021
Percentage of principal amount at which debt was issued (in hundredths)		100.00%
Maturity date		Jun. 01, 2031	Jun. 01, 2031
Aggregate principal amount		$ 650,000
Senior Notes Due2024 [Member]
Debt Instrument [Line Items]
Stated interest rate (in hundredths)		5.50%
Senior Notes Due2025 [Member]
Debt Instrument [Line Items]
Stated interest rate (in hundredths)		5.75%
Senior Notes [Member] | 5.875% Senior Notes due March 1, 2027 [Member]
Debt Instrument [Line Items]
Ownership interest in Suburban Energy Finance Corp (in hundredths)		100.00%
Stated interest rate (in hundredths)		5.875%
Date public offering completed		Feb. 14, 2017
Long-term borrowings		$ 350,000	$ 350,000
Percentage of principal amount at which debt was issued (in hundredths)		100.00%
Maturity date		Mar. 01, 2027
Aggregate principal amount		$ 350,000
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 described in the table below, 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%
Repurchase of debt due to decline in rating after consummation of change of control, period		90 days
Senior Notes [Member] | 7.375% Senior Notes due August 1, 2021 [Member]
Debt Instrument [Line Items]
Stated interest rate (in hundredths)		7.375%
Senior Notes [Member] | 5.0% Senior Notes due June 1, 2031 [Member]
Debt Instrument [Line Items]
Long-term borrowings		$ 650,000	$ 650,000
Percentage of the principal amount repurchase offer under change of control provision (in hundredths)			101.00%
Repurchase of debt due to decline in rating after consummation of change of control, period			90 days