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, 2014	$ (16,298)	$ (2,679)	$ (309)	$ (8,131)	$ (21,809)	$ 399	$ (31)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(667)	0	0	0	(671)	0	4
Other comprehensive income (loss)	36	0	0	0	0	36	0
Stock plans	440	2	39	481	0	0	0
Cash dividends	(614)	0	0	0	(614)	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders							0
Other	2	0	4	0	0	0	(2)
Ending balance at Dec. 31, 2015	(15,495)	(2,677)	(274)	(7,650)	(20,524)	363	(33)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(5,769)	0	0	0	(5,763)	0	(6)
Other comprehensive income (loss)	(91)	0	0	0	0	(91)	0
Stock plans	425	3	69	497	0	0	0
Cash dividends	(620)	0	0	0	(620)	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders							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 loss	(468)	0	0	0	(463)	0	(5)
Other comprehensive income (loss)	(15)	0	0	0	0	(15)	0
Stock plans	401	1	(6)	396	0	0	0
Cash dividends	(626)	0	0	0	(626)	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders							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