Lease Obligations - Summary of Leased Assets and Lease Liability Obligations (Parenthetical) (Detail) - USD ($) $ in Millions	Jul. 27, 2018	Mar. 31, 2019	Dec. 31, 2018
Lessee Lease Description [Line Items]
Finance lease liability		$ 72
Amazon Pipe-lay and Construction Vessel [Member]
Lessee Lease Description [Line Items]
Capital expenditure expected	$ 58
Property, plant and equipment, net		51	$ 52
Accumulated amortization,net		4	3
Finance lease liability		$ 52	$ 53
Amazon Pipe-lay and Construction Vessel [Member] | Minimum [Member]
Lessee Lease Description [Line Items]
Cost of modification including project management and other fees and expenses	260
Amazon Pipe-lay and Construction Vessel [Member] | Maximum [Member]
Lessee Lease Description [Line Items]
Cost of modification including project management and other fees and expenses	$ 290