Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Shareholders' equity activity [Roll Forward]
Beginning Balance	$ 9,524	$ 9,625	$ 9,544	$ 8,843	$ 8,391	$ 8,349	$ 9,544	$ 8,349
Net income (loss)	296	77	152	434	508	47	525	989
Other comprehensive income (loss)	0	1	1	7	1	(2)	2	6
Cash dividends	(158)	(157)	(157)	(157)	(158)	(158)
Stock repurchase program		(100)		(200)			(100)
Stock plans	90	83	87	91	104	127
Other	10	(5)	(2)	(1)	(3)	28
Ending Balance	$ 9,762	$ 9,524	$ 9,625	$ 9,017	$ 8,843	$ 8,391	9,762	9,017
Common Stock, Dividends, Per Share, Declared	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18
Common Shares
Shareholders' equity activity [Roll Forward]
Beginning Balance	$ 2,670	$ 2,671	$ 2,671	$ 2,672	$ 2,672	$ 2,673	2,671	2,673
Net income (loss)	0	0	0	0	0	0
Other comprehensive income (loss)	0	0	0	0	0	0
Cash dividends	0	0	0	0	0	0
Stock repurchase program		0		0
Stock plans	0	(1)	0	0	0	(1)
Other	0	0	0	0	0	0
Ending Balance	2,670	2,670	2,671	2,672	2,672	2,672	2,670	2,672
Paid-in Capital in Excess of Par Value
Shareholders' equity activity [Roll Forward]
Beginning Balance	58	224	211	125	222	207	211	207
Net income (loss)	0	0	0	0	0	0
Other comprehensive income (loss)	0	0	0	0	0	0
Cash dividends	0	0	0	0	0	0
Stock repurchase program		0		0
Stock plans	50	(166)	13	45	(97)	15
Other	0	0	0	0	0	0
Ending Balance	108	58	224	170	125	222	108	170
Treasury Stock
Shareholders' equity activity [Roll Forward]
Beginning Balance	(6,520)	(6,670)	(6,744)	(6,443)	(6,644)	(6,757)	(6,744)	(6,757)
Net income (loss)	0	0	0	0	0	0
Other comprehensive income (loss)	0	0	0	0	0	0
Cash dividends	0	0	0	0	0	0
Stock repurchase program		100		200
Stock plans	40	250	74	46	201	113
Other	0	0	0	0	0	0
Ending Balance	(6,480)	(6,520)	(6,670)	(6,597)	(6,443)	(6,644)	(6,480)	(6,597)
Retained Earnings
Shareholders' equity activity [Roll Forward]
Beginning Balance	13,652	13,734	13,739	12,939	12,586	12,668	13,739	12,668
Net income (loss)	295	75	152	435	511	46
Other comprehensive income (loss)	0	0	0	0	0	0
Cash dividends	(158)	(157)	(157)	(157)	(158)	(158)
Stock repurchase program		0		0
Stock plans	0	0	0	0	0	0
Other	11	0	0	(1)	0	30
Ending Balance	13,800	13,652	13,734	13,216	12,939	12,586	13,800	13,216
Accumulated Other Comprehensive Income (Loss)
Shareholders' equity activity [Roll Forward]
Beginning Balance	(352)	(354)	(355)	(470)	(471)	(469)	(355)	(469)
Net income (loss)	0	0	0	0	0	0
Other comprehensive income (loss)	0	1	1	7	1	(2)
Cash dividends	0	0	0	0	0	0
Stock repurchase program		0		0
Stock plans	0	0	0	0	0	0
Other	(1)	1	0	0	0	0
Ending Balance	(353)	(352)	(354)	(463)	(470)	(471)	(353)	(463)
Noncontrolling Interest in Consolidated Subsidiaries
Shareholders' equity activity [Roll Forward]
Beginning Balance	16	20	22	20	26	27	22	27
Net income (loss)	1	2	0	(1)	(3)	1
Other comprehensive income (loss)	0	0	0	0	0	0
Cash dividends	0	0	0	0	0	0
Stock repurchase program		0		0
Stock plans	0	0	0	0	0	0
Other	0	(6)	(2)	0	(3)	(2)
Ending Balance	$ 17	$ 16	$ 20	$ 19	$ 20	$ 26	$ 17	$ 19