Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Shareholders' equity activity [Roll Forward]
Beginning Balance	$ 8,025	$ 9,544
Net income (loss)	(1,015)	152
Other comprehensive income (loss)	11	1
Cash dividends	(158)	(157)
Stock repurchase program	(100)
Stock plans	(82)	(87)
Other	(2)	(2)
Ending Balance	$ 6,843	$ 9,625
Common Stock, Dividends, Per Share, Declared	$ 0.18	$ 0.18
Common Shares
Shareholders' equity activity [Roll Forward]
Beginning Balance	$ 2,669	$ 2,671
Net income (loss)	0	0
Other comprehensive income (loss)	0	0
Cash dividends	0	0
Stock repurchase program	0
Stock plans	0	0
Other	0	0
Ending Balance	2,669	2,671
Paid-in Capital in Excess of Par Value
Shareholders' equity activity [Roll Forward]
Beginning Balance	143	211
Net income (loss)	0	0
Other comprehensive income (loss)	0	0
Cash dividends	0	0
Stock repurchase program	0
Stock plans	(33)	(13)
Other	0	0
Ending Balance	110	224
Treasury Stock
Shareholders' equity activity [Roll Forward]
Beginning Balance	(6,427)	(6,744)
Net income (loss)	0	0
Other comprehensive income (loss)	0	0
Cash dividends	0	0
Stock repurchase program	100
Stock plans	(115)	(74)
Other	0	0
Ending Balance	(6,412)	(6,670)
Retained Earnings
Shareholders' equity activity [Roll Forward]
Beginning Balance	11,989	13,739
Net income (loss)	(1,017)	152
Other comprehensive income (loss)	0	0
Cash dividends	(158)	(157)
Stock repurchase program	0
Stock plans	0	0
Other	0	0
Ending Balance	10,814	13,734
Accumulated Other Comprehensive Income (Loss)
Shareholders' equity activity [Roll Forward]
Beginning Balance	(362)	(355)
Net income (loss)	0	0
Other comprehensive income (loss)	11	1
Cash dividends	0	0
Stock repurchase program	0
Stock plans	0	0
Other	0	0
Ending Balance	(351)	(354)
Noncontrolling Interest in Consolidated Subsidiaries
Shareholders' equity activity [Roll Forward]
Beginning Balance	13	22
Net income (loss)	2	0
Other comprehensive income (loss)	0	0
Cash dividends	0	0
Stock repurchase program	0
Stock plans	0	0
Other	(2)	(2)
Ending Balance	$ 13	$ 20