Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Leased Assets [Line Items]
Lessee, leases not yet commenced, amount	$ 70
Lessee, Operating Lease, Liability, Payments, Due Next Rolling Twelve Months	84
Lessee, Operating Lease, Liability, Payments, Due Year Two	71
Operating Lease, Payments	$ 77
Operating Lease, Weighted Average Remaining Lease Term	5 years 9 months 18 days
Operating Lease, Right-of-Use Asset	$ 336	$ 0	$ 0
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	137
Rent Expense, Net	80	92	$ 88
Leases, Future Minimum Payments Due, Next Twelve Months	73
Total leased assets	$ 67
Finance Lease, Weighted Average Remaining Lease Term	3.70%
Lessee, Operating Lease, Liability, Payments, Due Year Three	$ 59
Lessee, Operating Lease, Liability, Payments, Due Year Four	48
Lessee, Operating Lease, Liability, Payments, Due Year Five	41
Lessee, Operating Lease, Liability, Payments, Due after Year Five	79
Lessee, Operating Lease, Liability, Payments, Due	382
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	39
Operating Lease, Liability	343
Operating Leases, Future Minimum Payments, Due in Two Years	61
Operating Leases, Future Minimum Payments, Due in Three Years	47
Operating Leases, Future Minimum Payments, Due in Four Years	39
Operating Leases, Future Minimum Payments, Due in Five Years	31
Operating Leases, Future Minimum Payments, Due Thereafter	111
Operating Leases, Future Minimum Payments Due	362
Operating Lease, Liability, Noncurrent	$ 276	$ 0
Minimum [Member]
Operating Leased Assets [Line Items]
Lessee, Operating Lease, Term of Contract	1 year
Maximum [Member]
Operating Leased Assets [Line Items]
Lessee, Operating Lease, Term of Contract	60 years
Lessee, Operating and Finance Leases, Option to Extend	10 years
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	15 years