Leases (Supplemental Balance Sheet Information Related To Leases) (Details) $ in Millions	Dec. 31, 2019 USD ($)
Leases [Abstract]
Operating right-of-use assets	$ 204
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent
Finance right-of-use assets	$ 167
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:PropertyPlantAndEquipmentNet
Operating lease liabilities	$ 211
Finance lease liabilities	$ 167
Operating leases, Weighted-average remaining lease term	7 years 6 months 14 days
Operating leases, Weighted-average discount rate	8.25%
Finance lease, Weighted-average remaining lease term	9 years 1 month 6 days
Finance lease, Weighted-average discount rate	7.98%
Finance lease liabilities, Current	$ 25
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent
Financed lease liabilities, Noncurrent	$ 142
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent
Current operating lease liabilities	$ 44
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent
Noncurrent operating lease liabilities	$ 167
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent