Leases - Components of Lease Expense (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Finance lease cost:
Amortization of right-of-use assets	$ 15	$ 52
Interest on lease liabilities	2	7
Total finance lease cost	17	59
Operating lease cost	33	91
Sublease income		(2)
Total lease cost	$ 50	$ 148