Accounting Policies - Cumulative Effect of New Accounting Pronouncements (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Income Taxes — Asset	$ 1,527	$ 1,854	$ 1,847
Operating Lease ROU Assets	855	882	0
Property, Plant and Equipment		7,243	7,259
Operating Lease Liabilities due Within One Year	199	204	0
Operating Lease Liabilities	668	684	0
Long Term Debt and Finance Leases	4,753	5,124	5,110
Other Long Term Liabilities	508	465	471
Retained Earnings	$ 6,113	6,574	$ 6,597
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Income Taxes — Asset		7
Operating Lease ROU Assets		882
Property, Plant and Equipment		(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)