Lease Obligations - Schedule of Lease Cost (Detail) - USD ($) $ in Millions		3 Months Ended	9 Months Ended
		Sep. 30, 2019	Sep. 30, 2019
Finance lease cost
Net lease cost		$ 48	$ 126
SG&A Expenses [Member]
Lessee Lease Description [Line Items]
Operating lease cost	[1]	25	67
Cost of operations [Member]
Lessee Lease Description [Line Items]
Operating lease cost	[1]	21	51
Finance lease cost
Amortization of leased assets		1	4
Net Interest Expense [Member]
Finance lease cost
Interest on lease liabilities		$ 1	$ 4

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