Basis of Presentation - Recent Accounting Pronouncements (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Jan. 01, 2018	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification adjustment out of operating earnings		$ 338	$ 341	$ 770	$ 664
Reclassification adjustment to other expense		$ 0	$ 1	$ 9	$ 12
Forecast | Accounting Standards Update 2017-07, Year 2017 Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification adjustment out of operating earnings	$ 15
Reclassification adjustment to other expense	15
Forecast | Accounting Standards Update 2017-07, Year 2016 Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification adjustment out of operating earnings	29
Reclassification adjustment to other expense	$ 29