Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Shareholders' equity activity [Roll Forward]
Beginning Balance	$ 9,544	$ 8,349
Net income (loss)	152	47
Other comprehensive income (loss)	1	(2)
Cash dividends	(157)	(158)
Stock plans	87	127
Other	2	(28)
Ending Balance	$ 9,625	$ 8,391
Common Stock, Dividends, Per Share, Declared	$ 0.18	$ 0.18
Common Shares
Shareholders' equity activity [Roll Forward]
Beginning Balance	$ 2,671	$ 2,673
Net income (loss)	0	0
Other comprehensive income (loss)	0	0
Cash dividends	0	0
Stock plans	0	(1)
Other	0	0
Ending Balance	2,671	2,672
Paid-in Capital in Excess of Par Value
Shareholders' equity activity [Roll Forward]
Beginning Balance	211	207
Net income (loss)	0	0
Other comprehensive income (loss)	0	0
Cash dividends	0	0
Stock plans	13	15
Other	0	0
Ending Balance	224	222
Treasury Stock
Shareholders' equity activity [Roll Forward]
Beginning Balance	(6,744)	(6,757)
Net income (loss)	0	0
Other comprehensive income (loss)	0	0
Cash dividends	0	0
Stock plans	74	113
Other	0	0
Ending Balance	(6,670)	(6,644)
Retained Earnings
Shareholders' equity activity [Roll Forward]
Beginning Balance	13,739	12,668
Net income (loss)	152	46
Other comprehensive income (loss)	0	0
Cash dividends	(157)	(158)
Stock plans	0	0
Other	0	(30)
Ending Balance	13,734	12,586
Accumulated Other Comprehensive Income (Loss)
Shareholders' equity activity [Roll Forward]
Beginning Balance	(355)	(469)
Net income (loss)	0	0
Other comprehensive income (loss)	1	(2)
Cash dividends	0	0
Stock plans	0	0
Other	0	0
Ending Balance	(354)	(471)
Noncontrolling Interest in Consolidated Subsidiaries
Shareholders' equity activity [Roll Forward]
Beginning Balance	22	27
Net income (loss)	0	1
Other comprehensive income (loss)	0	0
Cash dividends	0	0
Stock plans	0	0
Other	2	2
Ending Balance	$ 20	$ 26