Lease Obligations - Schedule of Lease Cost (Detail) - USD ($) $ in Millions		3 Months Ended	6 Months Ended
		Jun. 30, 2019	Jun. 30, 2019
Finance lease cost
Net lease cost		$ 35	$ 78
SG&A Expenses [Member]
Lessee Lease Description [Line Items]
Operating lease cost	[1]	21	42
Cost of operations [Member]
Lessee Lease Description [Line Items]
Operating lease cost	[1]	11	30
Finance lease cost
Amortization of leased assets		1	3
Net Interest Expense [Member]
Finance lease cost
Interest on lease liabilities		$ 2	$ 3

[1] Includes short-term leases and immaterial variable lease costs.