Leases Leases (Narrative) (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating Lease, Cost	$ 75	$ 159
Variable Lease, Cost	11	25
Operating Lease, Payments	66	136
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	112	137
Lessee, Operating Lease, Lease Not yet Commenced, Value	$ 161	$ 161
Minimum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	3 years	3 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	15 years	15 years