Investment in Unconsolidated Subsidiary (Revenues and Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended
	Jun. 30, 2020	Jun. 27, 2020	Mar. 28, 2020	Jun. 30, 2019	Jun. 29, 2019	Mar. 30, 2019	Jun. 30, 2020	Jun. 27, 2020	Jun. 30, 2019	Jun. 29, 2019
Revenues:
Operating revenues		$ 848,673			$ 827,324			$ 1,701,515		$ 1,662,428
Expenses:
Cost of sales and operating expenses		632,347			644,716			1,279,255		1,295,629
Total costs and expenses		805,877			791,293			1,633,710		1,602,123
Operating income		106,288			74,124			229,117		122,675
Net income		$ 66,495	$ 86,091		$ 31,044	$ 19,640		$ 152,586		$ 50,684
Diamond Green Diesel Holdings LLC Joint Venture [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Revenues:
Operating revenues				$ 294,811					$ 597,529
Expenses:
Cost of sales and operating expenses				207,024					450,087
Depreciation, amortization and accretion expense				11,914					23,332
Total costs and expenses				218,938					473,419
Operating income				75,873					124,110
Other income				634					1,275
Interest and debt expense, net				(321)					(645)
Net income				$ 76,186					$ 124,740
Diamond Green Diesel Holdings LLC Joint Venture [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees | Subsequent Event
Revenues:
Operating revenues	$ 295,826						$ 654,441
Expenses:
Cost of sales and operating expenses	157,611						308,958
Depreciation, amortization and accretion expense	11,114						22,888
Total costs and expenses	168,725						331,846
Operating income	127,101						322,595
Other income	200						661
Interest and debt expense, net	(317)						(632)
Net income	$ 126,984						$ 322,624