Leases (Narrative) (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Leases [Abstract]
Lessee Operating And Finance Leases Remaining Lease Terms	13 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 3 months 18 days	4 years 3 months 18 days
Operating Lease, Weighted Average Discount Rate, Percent	5.00%	5.00%
Cash Paid for Amounts Included in the Measurement of Operating Lease Liabilities	$ 121	$ 121
Lessee, Operating Lease, Not Yet Commenced, Pending Right-of-Use Asset and Liability		$ 105
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	10 years	10 years