9. Members' Capital (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 27, 2020	Mar. 28, 2020	Jun. 29, 2019	Mar. 30, 2019	Jun. 27, 2020	Jun. 29, 2019
Beginning balance	$ 215,013	$ 202,837	$ 193,548	$ 219,756	$ 202,837	$ 219,756
Allocation of net income	101,204	12,176	24,748	10,538
Ending balance	266,138	$ 215,013	211,696	193,548	266,138	211,696
Class A Units [Member]
Allocation of net income	10,120		2,475		11,338	3,529
Member distributions	(5,008)		(660)	(3,675)
Class B Units [Member]
Allocation of net income	91,084		22,273		$ 102,042	$ 31,757
Member distributions	$ (45,071)		$ (5,940)	$ (33,071)