Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended					6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021		Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Shareholders' equity activity [Roll Forward]
Beginning Balance	$ 5,179	$ 4,983		$ 6,843	$ 8,025	$ 4,983	$ 8,025
Net income (loss)	230	171		(1,681)	(1,015)	401	(2,696)
Other comprehensive income (loss)	2			9	11	2	20
Cash dividends	(40)	(40)		(40)	(158)
Stock repurchase program					(100)
Stock plans	61	66		66	82
Other	3	1		1	2
Ending Balance	$ 5,429	$ 5,179		$ 5,196	$ 6,843	5,429	5,196
Common Stock, Dividends, Per Share, Declared	$ 0.045	$ 0.045		$ 0.18	$ 0.045
Common Shares
Shareholders' equity activity [Roll Forward]
Beginning Balance	$ 2,666	$ 2,666		$ 2,669	$ 2,669	2,666	2,669
Net income (loss)	0	0		0	0
Other comprehensive income (loss)	0			0	0
Cash dividends	0	0		0	0
Stock repurchase program					0
Stock plans	0	0		3	0
Other	0	0		0	0
Ending Balance	2,666	2,666		2,666	2,669	2,666	2,666
Paid-in Capital in Excess of Par Value
Shareholders' equity activity [Roll Forward]
Beginning Balance	34	0		110	143	0	143
Net income (loss)	0	0		0	0
Other comprehensive income (loss)	0			0	0
Cash dividends	0	0		0	0
Stock repurchase program					0
Stock plans	(8)	34		15	(33)
Other	0	0		0	0
Ending Balance	26	34		125	110	26	125
Treasury Stock
Shareholders' equity activity [Roll Forward]
Beginning Balance	(5,877)	(6,021)		(6,412)	(6,427)	(6,021)	(6,427)
Net income (loss)	0	0		0	0
Other comprehensive income (loss)	0			0	0
Cash dividends	0	0		0	0
Stock repurchase program					100
Stock plans	69	144		54	115
Other	0	0		0	0
Ending Balance	(5,808)	(5,877)		(6,358)	(6,412)	(5,808)	(6,358)
Retained Earnings
Shareholders' equity activity [Roll Forward]
Beginning Balance	8,709	8,691		10,814	11,989	8,691	11,989
Net income (loss)	227	170		(1,676)	(1,017)
Other comprehensive income (loss)	0			0	0
Cash dividends	(40)	(40)		(40)	(158)
Stock repurchase program					0
Stock plans	0	112	[1]	0	0
Other	0	0		0	0
Ending Balance	8,896	8,709		9,098	10,814	8,896	9,098
Accumulated Other Comprehensive Income (Loss)
Shareholders' equity activity [Roll Forward]
Beginning Balance	(362)	(362)		(351)	(362)	(362)	(362)
Net income (loss)	0	0		0	0
Other comprehensive income (loss)	2			9	11
Cash dividends	0	0		0	0
Stock repurchase program					0
Stock plans	0	0		0	0
Other	0	0		0	0
Ending Balance	(360)	(362)		(342)	(351)	(360)	(342)
Noncontrolling Interest in Consolidated Subsidiaries
Shareholders' equity activity [Roll Forward]
Beginning Balance	9	9		13	13	9	13
Net income (loss)	3	1		(5)	2
Other comprehensive income (loss)	0			0	0
Cash dividends	0	0		0	0
Stock repurchase program					0
Stock plans	0	0		0	0
Other	3	1		1	2
Ending Balance	$ 9	$ 9		$ 7	$ 13	$ 9	$ 7

[1] In January of 2021, we issued common stock from treasury shares for the employee stock purchase plan and for restricted stock grants. As a result, additional paid in capital in January of 2021 was reduced below zero, which resulted in a reduction of retained earnings by $112 million. Additional issuances from treasury shares could similarly impact additional paid in capital and retained earnings.