CONDENSED CONSOLIDATED STATEMENTS OF PARTNERS' CAPITAL (unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Unitholders [Member]	Accumulated Other Comprehensive (Loss) [Member]
Balance, beginning of period at Sep. 28, 2019	$ 423,938	$ 450,124	$ (26,186)
Balance (in units) at Sep. 28, 2019		61,735
Net income	117,524	$ 117,524
Other comprehensive income	1,082		1,082
Partnership distributions	(74,283)	(74,283)
Common Units issued under Restricted Unit Plans	(1,761)	$ (1,761)
Common Units issued under Restricted Unit Plans (in units)		338
Recognition in earnings of net actuarial loss for pension settlement	0
Compensation costs recognized under Restricted Unit Plans	4,822	$ 4,822
Balance, end of period at Mar. 28, 2020	471,322	$ 496,426	(25,104)
Balance (in units) at Mar. 28, 2020		62,073
Balance, beginning of period at Dec. 28, 2019	428,434	$ 454,079	(25,645)
Balance (in units) at Dec. 28, 2019		62,070
Net income	77,361	$ 77,361
Other comprehensive income	541		541
Partnership distributions	(37,242)	(37,242)
Common Units issued under Restricted Unit Plans	(32)	$ (32)
Common Units issued under Restricted Unit Plans (in units)		3
Recognition in earnings of net actuarial loss for pension settlement	0
Compensation costs recognized under Restricted Unit Plans	2,260	$ 2,260
Balance, end of period at Mar. 28, 2020	471,322	$ 496,426	(25,104)
Balance (in units) at Mar. 28, 2020		62,073
Balance, beginning of period at Sep. 26, 2020	362,381	$ 388,157	(25,776)
Balance (in units) at Sep. 26, 2020		62,146
Net income	165,193	$ 165,193
Other comprehensive income	1,186		1,186
Partnership distributions	(37,401)	(37,401)
Common Units issued under Restricted Unit Plans	(1,534)	$ (1,534)
Common Units issued under Restricted Unit Plans (in units)		383
Recognition in earnings of net actuarial loss for pension settlement	570		570
Compensation costs recognized under Restricted Unit Plans	4,953	$ 4,953
Balance, end of period at Mar. 27, 2021	495,348	$ 519,368	(24,020)
Balance (in units) at Mar. 27, 2021		62,529
Balance, beginning of period at Dec. 26, 2020	383,162	$ 408,345	(25,183)
Balance (in units) at Dec. 26, 2020		62,522
Net income	127,216	$ 127,216
Other comprehensive income	593		593
Partnership distributions	(18,757)	(18,757)
Common Units issued under Restricted Unit Plans	(31)	$ (31)
Common Units issued under Restricted Unit Plans (in units)		7
Recognition in earnings of net actuarial loss for pension settlement	570		570
Compensation costs recognized under Restricted Unit Plans	2,595	$ 2,595
Balance, end of period at Mar. 27, 2021	$ 495,348	$ 519,368	$ (24,020)
Balance (in units) at Mar. 27, 2021		62,529