Leases Leases (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($) Rate	Jun. 30, 2019 USD ($) Rate
Assets and Liabilities, Lessee [Abstract]
Operating Lease, Right-of-Use Asset	$ 252	$ 252
Operating Lease, Liability, Current	56	56
Operating Lease, Liability, Noncurrent	205	205
Lessee, Lease, Description [Line Items]
Lessee, leases not yet commenced, amount	63	63
Operating Lease, Payments		35
Operating Lease, Cost	$ 18	$ 36
Operating Lease, Weighted Average Remaining Lease Term	5 years 3 months 29 days	5 years 3 months 29 days
Finance Lease, Weighted Average Discount Rate, Percent | Rate	3.62%	3.62%
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	$ 37	$ 37
Lessee, Operating Lease, Liability, Payments, Due Year Two	64	64
Lessee, Operating Lease, Liability, Payments, Due Year Three	52	52
Lessee, Operating Lease, Liability, Payments, Due Year Four	41	41
Lessee, Operating Lease, Liability, Payments, Due Year Five	31	31
Lessee, Operating Lease, Liability, Payments, Due after Year Five	65	65
Lessee, Operating Lease, Liability, Payments, Due	289	289
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	28	28
Operating Lease, Liability	$ 261	$ 261
Minimum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	5 months	5 months
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