Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Receivables, allowances	$ 20	$ 25
Common stock, shares issued (in shares)	2,109,316,331	2,109,316,331
Repurchased stock, shares (in shares)	553,421,668	554,736,610