Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Shares	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, 2015	$ 15,495	$ 2,677	$ 274	$ (7,650)	$ 20,524	$ (363)	$ 33
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(5,769)	0	0	0	(5,763)	0	(6)
Other comprehensive income (loss)	(91)	0	0	0	0	(91)	0
Cash dividends	(620)	0	0	0	(620)	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders							0
Stock plans	425	(3)	(69)	497	0	0	0
Other	(8)	0	4	0	0	0	(12)
Ending 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
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders							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 earnigs 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
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders							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