Leases (Narrative) (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
Leases [Abstract]
Lessee Operating And Finance Leases Remaining Lease Terms	19 years
Operating And Finance Leases, Options To Extend Lease Terms	20 years
Operating And Finance Leases, Options To Terminate Lease Term	1 year
Operating Lease, Weighted Average Remaining Lease Term	4 years 4 months 24 days	4 years 4 months 24 days
Operating Lease, Weighted Average Discount Rate, Percent	5.20%	5.20%
Cash Paid for Amounts Included in the Measurement of Operating Lease Liabilities	$ 80	$ 80
Lessee, Operating Lease, Not Yet Commenced, Pending Right-of-Use Asset and Liability		$ 96
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	7 years	7 years