Leases Leases (Narrative) (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Lessee Disclosure [Abstract]
Operating Lease, Cost	$ 82	$ 241
Variable Lease, Cost	15	40
Operating Lease, Payments	70	205
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	177	315
Lessee, Operating Lease, Lease Not yet Commenced, Value	$ 160	$ 160
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	15 years	15 years