Leases (Supplemental Balance Sheet Information Related To Leases) (Details) $ in Millions	Mar. 31, 2019 USD ($)
Supplemental Balance Sheet Information Related To Leases [Line Items]
Operating right-of-use assets	$ 203
Finance right-of-use assets	185
Operating lease liabilities	208
Finance lease liabilities	$ 185
Operating leases, Weighted-average remaining lease term	7 years 9 months 15 days
Operating leases, Weighted-average discount rate	8.37%
Weighted-average remaining lease term	9 years 10 months 13 days
Finance lease, Weighted-average discount rate	7.95%
Other Current Liabilities [Member]
Supplemental Balance Sheet Information Related To Leases [Line Items]
Finance lease liabilities, Current	$ 35
Current operating lease liabilities	45
Other Noncurrent Liabilities [Member]
Supplemental Balance Sheet Information Related To Leases [Line Items]
Financed lease liabilities, Noncurrent	150
Noncurrent operating lease liabilities	$ 163