Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	4 Months Ended
	Apr. 20, 2019	Apr. 21, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 65,866	$ 51,247
Pension and postretirement plans:
Settlement loss		3,490
Net gain for the period		8,813
Amortization of prior service cost included in net income	79	26
Amortization of actuarial loss included in net income	1,569	1,076
Pension and postretirement plans, net of tax	1,648	13,405
Derivative instruments:
Net change in fair value of derivatives	(9,593)	10,470
(Gain) loss reclassified to net income	(2,178)	297
Derivative instruments, net of tax	(11,771)	10,767
Other comprehensive income (loss), net of tax	(10,123)	24,172
Comprehensive income	$ 55,743	$ 75,419