Benefit Plans - Reconciliation of Benefit Obligation (Detail) - Postretirement Benefits [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Jan. 01, 2017	Jan. 03, 2016
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	$ 85,255	$ 70,361
Service cost	2,232	1,567	$ 1,118
Interest cost	3,636	3,094	2,878
Acquisition of benefits	3,291	3,458
Plan participants’ contributions	752	662
Actuarial (gain)/loss	1,796	9,152
Benefits paid	(2,994)	(3,135)
Medicare Part D subsidy reimbursement	37	96
Divestiture of benefits related to the Deep South and Somerset Exchange Business and the Florence and Laurel Distribution Business	(17,340)
Benefit obligation at end of year	$ 76,665	$ 85,255	$ 70,361