Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jul. 16, 2016	Jul. 18, 2015	Jul. 16, 2016	Jul. 18, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income		$ 51,155	$ 51,760	$ 110,518	$ 113,149
Pension and postretirement plans:
Settlement loss		2,854		2,854
Net gain (loss) for the period		(36,407)		(36,407)
Amortization of prior service cost (credit) included in net income		17	(67)	50	(156)
Amortization of actuarial loss included in net income		646	624	1,666	1,456
Pension and postretirement plans, net of tax		(32,890)	557	(31,837)	1,300
Derivative instruments:
Net change in fair value of derivatives	[1]	(3,525)	5,818	(937)	1,390
Loss reclassified to net income		803	1,251	1,946	2,838
Derivative instruments, net of tax		(2,722)	7,069	1,009	4,228
Other comprehensive income (loss), net of tax		(35,612)	7,626	(30,828)	5,528
Comprehensive income		$ 15,543	$ 59,386	$ 79,690	$ 118,677

[1] Amounts in parentheses indicate debits to determine net income.