Accounting Policies - Schedule of Changes in Accounting Policy (Details) - USD ($) $ in Millions	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Income Taxes	$ 1,864	$ 1,854	$ 1,847
Operating Lease Right-of-Use Assets	862	882	0
Property, Plant and Equipment, less Accumulated Depreciation	7,196	7,243	7,259
Operating Lease Liabilities due Within One Year	203	204	0
Operating Lease Liabilities	667	684	0
Long Term Debt and Finance Leases	5,545	5,124	5,110
Other Long Term Liabilities	550	465	471
Retained Earnings	$ 6,476	6,574	6,597
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Income Taxes		7
Operating Lease Right-of-Use Assets		882
Property, Plant and Equipment, less Accumulated Depreciation		(16)
Operating Lease Liabilities due Within One Year		204
Operating Lease Liabilities		684
Long Term Debt and Finance Leases		14
Other Long Term Liabilities		(6)
Retained Earnings		$ (23)	$ (23)