Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Shareholders' equity activity [Roll Forward]
Beginning Balance	$ 6,843	$ 8,025	$ 9,625	$ 9,544	$ 8,025	$ 9,544
Net income (loss)	(1,681)	(1,015)	77	152	(2,696)	229
Other comprehensive income (loss)	9	11	1	1	20	2
Cash dividends	(40)	(158)	(157)	(157)
Stock repurchase program		(100)	(100)		(100)
Stock plans	66	82	83	87
Other	(1)	(2)	(5)	(2)
Ending Balance	$ 5,196	$ 6,843	$ 9,524	$ 9,625	5,196	9,524
Common Stock, Dividends, Per Share, Declared	$ 0.045	$ 0.18	$ 0.18	$ 0.18
Common Shares
Shareholders' equity activity [Roll Forward]
Beginning Balance	$ 2,669	$ 2,669	$ 2,671	$ 2,671	2,669	2,671
Net income (loss)	0	0	0	0
Other comprehensive income (loss)	0	0	0	0
Cash dividends	0	0	0	0
Stock repurchase program		0	0
Stock plans	3	0	1	0
Other	0	0	0	0
Ending Balance	2,666	2,669	2,670	2,671	2,666	2,670
Paid-in Capital in Excess of Par Value
Shareholders' equity activity [Roll Forward]
Beginning Balance	110	143	224	211	143	211
Net income (loss)	0	0	0	0
Other comprehensive income (loss)	0	0	0	0
Cash dividends	0	0	0	0
Stock repurchase program		0	0
Stock plans	15	33	166	13
Other	0	0	0	0
Ending Balance	125	110	58	224	125	58
Treasury Stock
Shareholders' equity activity [Roll Forward]
Beginning Balance	(6,412)	(6,427)	(6,670)	(6,744)	(6,427)	(6,744)
Net income (loss)	0	0	0	0
Other comprehensive income (loss)	0	0	0	0
Cash dividends	0	0	0	0
Stock repurchase program		100	100
Stock plans	54	115	250	74
Other	0	0	0	0
Ending Balance	(6,358)	(6,412)	(6,520)	(6,670)	(6,358)	(6,520)
Retained Earnings
Shareholders' equity activity [Roll Forward]
Beginning Balance	10,814	11,989	13,734	13,739	11,989	13,739
Net income (loss)	(1,676)	(1,017)	75	152
Other comprehensive income (loss)	0	0	0	0
Cash dividends	(40)	(158)	(157)	(157)
Stock repurchase program		0	0
Stock plans	0	0	0	0
Other	0	0	0	0
Ending Balance	9,098	10,814	13,652	13,734	9,098	13,652
Accumulated Other Comprehensive Income (Loss)
Shareholders' equity activity [Roll Forward]
Beginning Balance	(351)	(362)	(354)	(355)	(362)	(355)
Net income (loss)	0	0	0	0
Other comprehensive income (loss)	9	11	1	1
Cash dividends	0	0	0	0
Stock repurchase program		0	0
Stock plans	0	0	0	0
Other	0	0	1	0
Ending Balance	(342)	(351)	(352)	(354)	(342)	(352)
Noncontrolling Interest in Consolidated Subsidiaries
Shareholders' equity activity [Roll Forward]
Beginning Balance	13	13	20	22	13	22
Net income (loss)	(5)	2	2	0
Other comprehensive income (loss)	0	0	0	0
Cash dividends	0	0	0	0
Stock repurchase program		0	0
Stock plans	0	0	0	0
Other	(1)	(2)	(6)	(2)
Ending Balance	$ 7	$ 13	$ 16	$ 20	$ 7	$ 16