Accumulated Other Comprehensive Income (Loss) - Summary of Accumulated Other Comprehensive (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Jan. 01, 2017	Jan. 03, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 363,024	$ 322,432	$ 256,943
Gains (Losses) During the Period, Pre-tax Activity	(13,015)	(18,929)	9,112
Gains (Losses) During the Period, Tax Effect	3,211	7,287	(3,490)
Reclassification to income, Pre-tax Activity	11,687	1,874	3,061
Reclassification to income, Tax Effect	(3,188)	(722)	(1,176)
Ending Balance	458,907	363,024	322,432
Deep South and Somerset Exchange Business and the Florence and Laurel Distribution Business [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification to income, Pre-tax Activity	8,257
Reclassification to income, Tax Effect	(2,037)
Ending Balance	6,220
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(11)	(5)	(1)
Reclassification to income, Pre-tax Activity	40	(11)	(8)
Reclassification to income, Tax Effect	(15)	5	4
Ending Balance	14	(11)	(5)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(92,897)	(82,407)	(89,914)
Ending Balance	(94,202)	(92,897)	(82,407)
Net Pension Activity [Member] | Actuarial Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(72,393)	(68,243)	(74,867)
Gains (Losses) During the Period, Pre-tax Activity	(11,219)	(9,777)	7,513
Gains (Losses) During the Period, Tax Effect	2,768	3,764	(2,877)
Reclassification to income, Pre-tax Activity	3,402	3,031	3,230
Reclassification to income, Tax Effect	(1,176)	(1,168)	(1,242)
Ending Balance	(78,618)	(72,393)	(68,243)
Net Pension Activity [Member] | Prior Service Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(61)	(78)	(99)
Reclassification to income, Pre-tax Activity	28	28	35
Reclassification to income, Tax Effect	(10)	(11)	(14)
Ending Balance	(43)	(61)	(78)
Net Postretirement Benefits Activity [Member] | Actuarial Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(24,111)	(19,825)	(22,759)
Gains (Losses) During the Period, Pre-tax Activity	(1,796)	(9,152)	1,599
Gains (Losses) During the Period, Tax Effect	443	3,523	(613)
Reclassification to income, Pre-tax Activity	2,942	2,186	3,164
Reclassification to income, Tax Effect	(997)	(843)	(1,216)
Ending Balance	(23,519)	(24,111)	(19,825)
Net Postretirement Benefits Activity [Member] | Prior Service Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	3,679	5,744	7,812
Reclassification to income, Pre-tax Activity	(2,982)	(3,360)	(3,360)
Reclassification to income, Tax Effect	1,047	1,295	1,292
Ending Balance	$ 1,744	$ 3,679	$ 5,744