Leases Leases (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($) Rate	Sep. 30, 2019 USD ($) Rate
Assets and Liabilities, Lessee [Abstract]
Operating Lease, Right-of-Use Asset	$ 306	$ 306
Operating Lease, Liability, Current	62	62
Operating Lease, Liability, Noncurrent	251	251
Lessee, Lease, Description [Line Items]
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability		84
Lessee, leases not yet commenced, amount	68	68
Operating Lease, Payments		55
Operating Lease, Cost	$ 21	$ 57
Operating Lease, Weighted Average Remaining Lease Term	5 years 7 months 6 days	5 years 7 months 6 days
Finance Lease, Weighted Average Discount Rate, Percent | Rate	3.70%	3.70%
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	$ 22	$ 22
Lessee, Operating Lease, Liability, Payments, Due Year Two	76	76
Lessee, Operating Lease, Liability, Payments, Due Year Three	65	65
Lessee, Operating Lease, Liability, Payments, Due Year Four	52	52
Lessee, Operating Lease, Liability, Payments, Due Year Five	41	41
Lessee, Operating Lease, Liability, Payments, Due after Year Five	95	95
Lessee, Operating Lease, Liability, Payments, Due	350	350
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	37	37
Operating Lease, Liability	$ 314	$ 314
Minimum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	1 month	1 month
Lessee, Operating Lease, Term of Contract	1 year	1 year
Maximum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	15 years	15 years
Lessee, Operating Lease, Term of Contract	60 years	60 years
Lessee, Operating and Finance Leases, Option to Extend		10 years