Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock	Paid-in Capital in Excess of Par Value	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest in Consolidated Subsidiaries
Beginning balance at Dec. 31, 2016	$ 9,448	$ 2,674	$ 201	$ (7,153)	$ 14,141	$ (454)	$ 39
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(468)	0	0	0	(463)	0	(5)
Other comprehensive income (loss)	(15)	0	0	0	0	(15)	0
Cash dividends	(626)	0	0	0	(626)	0
Cash dividends - Noncontrolling interest							0
Stock plans	401	(1)	6	396	0	0	0
Other	(7)	0	0	0	0	0	(7)
Ending balance at Dec. 31, 2017	8,349	2,673	207	(6,757)	12,668	(469)	27
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained earnings adjustment for new accounting standard	(384)	0	0	0	(384)	0	0
Net income (loss)	1,657	0	0	0	1,656	0	1
Other comprehensive income (loss)	114	0	0	0	0	114	0
Cash dividends	(630)	0	0	0	(630)	0
Cash dividends - Noncontrolling interest							0
Stock plans	415	(2)	4	413	0	0	0
Stock repurchase program	(400)	0	0	(400)	0	0	0
Other	39	0	0	0	45	0	(6)
Ending balance at Dec. 31, 2018	9,544	2,671	211	(6,744)	13,739	(355)	22
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(1,129)	0	0	0	(1,131)	0	2
Other comprehensive income (loss)	(8)	0	0	0	0	(8)	0
Cash dividends	(630)	0	0	0	(630)	0
Cash dividends - Noncontrolling interest							0
Stock plans	348	(2)	(67)	417	0	0	0
Stock repurchase program	(100)	0	0	(100)	0	0	0
Other	0	0	(1)	0	11	1	(11)
Ending balance at Dec. 31, 2019	$ 8,025	$ 2,669	$ 143	$ (6,427)	$ 11,989	$ (362)	$ 13