Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 136	$ 157
Accumulated depreciation	(6,190)	(6,825)
Finite-lived intangible assets, accumulated amortization	$ 527	$ 476
Common stock, par value (USD per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	250,000,000	250,000,000
Common stock, shares issued (in shares)	112,000,000	112,000,000
Common stock, shares outstanding (in shares)	64,000,000	71,000,000
Treasury stock shares (in shares)	48,000,000	41,000,000