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. 30, 2017	$ 552,982	$ 581,794	$ (28,812)
Balance (in units) at Sep. 30, 2017		61,105
Net income	143,955	$ 143,955
Other comprehensive income	1,514		1,514
Partnership distributions	(73,499)	(73,499)
Common Units issued under Restricted Unit Plans	(846)	$ (846)
Common Units issued under Restricted Unit Plans (in units)		299
Compensation costs recognized under Restricted Unit Plans	5,147	$ 5,147
Balance, end of period at Mar. 31, 2018	629,253	$ 656,551	(27,298)
Balance (in units) at Mar. 31, 2018		61,404
Balance, beginning of period at Dec. 30, 2017	556,047	$ 584,102	(28,055)
Balance (in units) at Dec. 30, 2017		61,389
Net income	106,787	$ 106,787
Other comprehensive income	757		757
Partnership distributions	(36,836)	(36,836)
Common Units issued under Restricted Unit Plans	0	$ 0
Common Units issued under Restricted Unit Plans (in units)		15
Compensation costs recognized under Restricted Unit Plans	2,498	$ 2,498
Balance, end of period at Mar. 31, 2018	629,253	$ 656,551	(27,298)
Balance (in units) at Mar. 31, 2018		61,404
Balance, beginning of period at Sep. 29, 2018	493,824	$ 518,494	(24,670)
Balance (in units) at Sep. 29, 2018		61,405
Net income	148,735	$ 148,735
Other comprehensive income	1,104		1,104
Partnership distributions	(73,841)	(73,841)
Common Units issued under Restricted Unit Plans	(1,349)	$ (1,349)
Common Units issued under Restricted Unit Plans (in units)		259
Compensation costs recognized under Restricted Unit Plans	6,575	$ 6,575
Balance, end of period at Mar. 30, 2019	575,048	$ 598,614	(23,566)
Balance (in units) at Mar. 30, 2019		61,664
Balance, beginning of period at Dec. 29, 2018	486,924	$ 511,042	(24,118)
Balance (in units) at Dec. 29, 2018		61,664
Net income	121,016	$ 121,016
Other comprehensive income	552		552
Partnership distributions	(36,998)	(36,998)
Common Units issued under Restricted Unit Plans	0	$ 0
Common Units issued under Restricted Unit Plans (in units)		0
Compensation costs recognized under Restricted Unit Plans	3,554	$ 3,554
Balance, end of period at Mar. 30, 2019	$ 575,048	$ 598,614	$ (23,566)
Balance (in units) at Mar. 30, 2019		61,664