Supplemental Financial Information - Shareholder tax on repurchased shares (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 29, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Shareholder tax on repurchased shares	$ 2	$ 155	$ (62)	$ (353)	$ 127