Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 18	$ 17
Preferred stock:
Shares issued	0	0
Shares outstanding	0	0
Par value	$ 0.01
Shares authorized	30
Common stock:
Shares issued	979	978
Par value	$ 0.01
Shares authorized	2,000
Treasury stock	(329)	(329)

Amount of allowance for credit loss on accounts receivable, classified as current.

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