CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Accounts receivable, allowance	$ 99	$ 106
PP&E, accumulated depreciation	$ 29,814	$ 29,346
Preferred stock-non-redeemable, par value (in dollars per share)	$ 25.00	$ 25.00
Preferred stock-non-redeemable, shares authorized (in shares)	2,000,000	2,000,000
Preferred stock-non-redeemable, shares issued (in shares)	7,000	7,000
Preferred stock-non-redeemable, shares outstanding (in shares)	7,000	7,000
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00
Common stock, shares authorized (in shares)	2,200,000,000	2,200,000,000
Common stock, shares issued (in shares)	1,097,711,000	1,090,058,000
Common stock, shares outstanding (in shares)	1,097,711,000	1,090,058,000