Comprehensive Income Reclassifications (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2016	Oct. 01, 2016	Jul. 02, 2016	Apr. 02, 2016	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net sales		$ 853,130	$ 812,576	$ 846,646	$ 875,374	$ 952,549	$ 936,262	$ 894,930	$ 878,510	$ 3,387,726	$ 3,662,251	$ 3,391,928
Cost of sales and operating expenses										2,647,083	2,875,443	2,635,333
Amortization of prior service cost										(35)	(35)	(36)
Amortization of actuarial loss										3,543	4,786	4,632
Amortization of curtailment										498
Amortization of settlement										(3)	42	(114)
Income taxes										(12,031)	69,154	(15,315)
Net income		$ 40,648	$ (6,037)	$ (30,420)	$ 97,305	$ 105,729	$ 7,761	$ 9,149	$ 5,829	101,496	128,468	102,313
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income										(1,741)	159	(434)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] | Soybean Meal [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net sales										8	0	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivative Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income from operations before income taxes										1,906	5,220	3,868
Income taxes										(492)	(2,025)	(1,501)
Net income										1,414	3,195	2,367
Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivative Instruments | Natural Gas Swap [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales and operating expenses										(14)	(35)	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivative Instruments | Corn Option [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales and operating expenses										1,912	5,255	3,868
Reclassification out of Accumulated Other Comprehensive Income [Member] | Defined Benefit Pension Plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of prior service cost	[1]									(35)	(35)	(36)
Amortization of actuarial loss	[1]									(3,543)	(4,786)	(4,632)
Amortization of curtailment	[1]									(498)	0	0
Amortization of settlement	[1]									3	(42)	114
Income from operations before income taxes										(4,073)	(4,863)	(4,554)
Income taxes										918	1,827	1,753
Net income										$ (3,155)	$ (3,036)	$ (2,801)

[1] These items are included in the computation of net periodic pension cost. See Note 15 Employee Benefit Plans for additional information.