Accounting Policies - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ 6,476	$ 6,574	$ 6,597
Long term debt and finance leases	5,545	5,124	5,110
Property, plant and equipment, less accumulated depreciation	7,196	7,243	7,259
Deferred income taxes	1,864	1,854	1,847
Other liabilities, noncurrent	$ 550	465	471
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings		(23)	$ (23)
Long term debt and finance leases		14
Property, plant and equipment, less accumulated depreciation		(16)
Deferred income taxes		7
Other liabilities, noncurrent		$ (6)