CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable, allowance	$ 153	$ 164
PP&E, accumulated depreciation	$ 26,493	$ 24,352
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)	1,600,000,000	1,600,000,000
Common stock, shares issued (in shares)	1,080,573,000	1,069,169,000
Common stock, shares outstanding (in shares)	1,080,573,000	1,069,169,000