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

[1] In January 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 2021 was reduced below zero, which resulted in a reduction of retained earnings by $112 million. Additional issuances from treasury shares will similarly impact additional paid in capital and retained earnings.