Postretirement Plans - Additional Information (Detail) - USD ($)				3 Months Ended			4 Months Ended	9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Oct. 06, 2018	Jul. 14, 2018	Oct. 07, 2017	Apr. 21, 2018	Oct. 06, 2018	Oct. 07, 2017	Dec. 30, 2017
Pension and Other Postretirement Benefits Disclosure [Line Items]
Defined benefit plans estimated final non-cash settlement charge				$ 125,000,000				$ 125,000,000
Discount rate used to derive estimated plan				3.47%				3.47%
Expected long-term rate of return on plan assets	5.20%	5.90%	5.90%
Total cost and employer contributions				$ 6,000,000		$ 6,500,000		$ 19,600,000	$ 22,000,000
Multiemployer plan, withdrawal obligation						$ 15,200,000			$ 15,200,000	$ 15,223,000
Multiemployer plans, increase in withdrawal obligation							$ 2,300,000
Multiemployer plans transition payments payable				3,100,000				$ 3,100,000
Multiemployer plans payable date								Nov. 03, 2017
Multiemployer plan withdrawal liability of net present value monthly payments period						20 years
Multiemployer plan, withdrawal obligation paid							200,000
Plan No. 1
Pension and Other Postretirement Benefits Disclosure [Line Items]
Voluntarily contributions made by an employer				100,000	$ 30,000,000		$ 10,000,000
Plan No. 2
Pension and Other Postretirement Benefits Disclosure [Line Items]
Voluntarily contributions made by an employer				600,000
Minimum [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Required cash contribution to fully fund under defined benefit plans				5,000,000				$ 5,000,000
Maximum
Pension and Other Postretirement Benefits Disclosure [Line Items]
Required cash contribution to fully fund under defined benefit plans				$ 35,000,000				$ 35,000,000