Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Allowance for Accounts Receivable	$ 141	$ 150
Accumulated Depreciation	$ 11,192	$ 10,991
Common Stock, par value (in dollars per share)
Common Stock, shares authorized (in shares)	450,000,000	450,000,000
Common Stock, shares outstanding (in shares)	281,000,000	233,000,000