Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Shareholders' equity activity [Roll Forward]
Beginning Balance	$ 5,196	$ 6,843	$ 8,025	$ 9,524	$ 9,625	$ 9,544	$ 8,025	$ 9,544
Net income (loss)	(19)	(1,681)	(1,015)	296	77	152	(2,715)	525
Other comprehensive income (loss)	2	9	11	0	1	1	22	2
Cash dividends	(40)	(40)	(158)	(158)	(157)	(157)
Stock repurchase program			(100)		(100)		(100)
Stock plans	120	66	82	90	83	87
Other	56	1	2	(10)	5	2
Ending Balance	$ 5,203	$ 5,196	$ 6,843	$ 9,762	$ 9,524	$ 9,625	5,203	9,762
Common Stock, Dividends, Per Share, Declared	$ 0.045	$ 0.045	$ 0.18	$ 0.18	$ 0.18	$ 0.18
Common Shares
Shareholders' equity activity [Roll Forward]
Beginning Balance	$ 2,666	$ 2,669	$ 2,669	$ 2,670	$ 2,671	$ 2,671	2,669	2,671
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	3	0	0	1	0
Other	0	0	0	0	0	0
Ending Balance	2,666	2,666	2,669	2,670	2,670	2,671	2,666	2,670
Paid-in Capital in Excess of Par Value
Shareholders' equity activity [Roll Forward]
Beginning Balance	125	110	143	58	224	211	143	211
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	102	15	33	50	166	13
Other	0	0	0	0	0	0
Ending Balance	23	125	110	108	58	224	23	108
Treasury Stock
Shareholders' equity activity [Roll Forward]
Beginning Balance	(6,358)	(6,412)	(6,427)	(6,520)	(6,670)	(6,744)	(6,427)	(6,744)
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		100
Stock plans	222	54	115	40	250	74
Other	0	0	0	0	0	0
Ending Balance	(6,136)	(6,358)	(6,412)	(6,480)	(6,520)	(6,670)	(6,136)	(6,480)
Retained Earnings
Shareholders' equity activity [Roll Forward]
Beginning Balance	9,098	10,814	11,989	13,652	13,734	13,739	11,989	13,739
Net income (loss)	(17)	(1,676)	(1,017)	295	75	152
Other comprehensive income (loss)	0	0	0	0	0	0
Cash dividends	(40)	(40)	(158)	(158)	(157)	(157)
Stock repurchase program			0		0
Stock plans	0	0	0	0	0	0
Other	54	0	0	(11)	0	0
Ending Balance	8,987	9,098	10,814	13,800	13,652	13,734	8,987	13,800
Accumulated Other Comprehensive Income (Loss)
Shareholders' equity activity [Roll Forward]
Beginning Balance	(342)	(351)	(362)	(352)	(354)	(355)	(362)	(355)
Net income (loss)	0	0	0	0	0	0
Other comprehensive income (loss)	2	9	11	0	1	1
Cash dividends	0	0	0	0	0	0
Stock repurchase program			0		0
Stock plans	0	0	0	0	0	0
Other	0	0	0	1	(1)	0
Ending Balance	(340)	(342)	(351)	(353)	(352)	(354)	(340)	(353)
Noncontrolling Interest in Consolidated Subsidiaries
Shareholders' equity activity [Roll Forward]
Beginning Balance	7	13	13	16	20	22	13	22
Net income (loss)	(2)	(5)	2	1	2	0
Other comprehensive income (loss)	0	0	0	0	0	0
Cash dividends				0
Cash dividends	0	0	0		0	0
Stock repurchase program			0		0
Stock plans	0	0	0	0	0	0
Other	2	1	2	0	6	2
Ending Balance	$ 3	$ 7	$ 13	$ 17	$ 16	$ 20	$ 3	$ 17