Leases - Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Operating Leases
Operating Lease ROU Assets	$ 862	$ 882	$ 0
Operating Lease Liabilities due Within One Year	203	204	0
Operating Lease Liabilities	667	$ 684	0
Total Operating Lease Liabilities	870
Finance Leases
Property, Plant and Equipment, at cost	263
Accumulated Depreciation	52
Property, Plant and Equipment, net	211
Long Term Debt and Finance Leases due Within One Year	5
Long Term Debt and Finance Leases	240
Total Finance Lease Liabilities	$ 245		$ 37
Weighted Average Remaining Lease Term
Operating Leases	6 years 10 months 24 days
Finance Leases	32 years 4 months 24 days
Weighted Average Discount Rate
Operating Leases	6.71%
Finance Leases	8.44%