Shareholders' Equity (Shareholders' Equity Activity) (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2017
Schedule of Issued and Treasury Shares [Line Items]
Capital in Excess of Par Value	$ 6,676			$ 6,655
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning balance	(571)	$ 2,068
Net Income (Loss)	(242)	(443)
Other Comprehensive Income	5	43
Dividends Paid to Noncontrolling Interests	(4)	(5)
Equity Awards Granted, Vested and Exercised	17	28
Balance, ending balance	(898)	1,691	$ 2,068
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	(97)
Stockholders' Equity, Other	(6)
Par Value of Issued Shares
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning balance	1	1
Equity Awards Granted, Vested and Exercised	0	0
Balance, ending balance	1	1	1
Capital in Excess of Par Value
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning balance	6,655	6,571
Equity Awards Granted, Vested and Exercised	17	28
Balance, ending balance	6,676	6,599	$ 6,571
Stock issued during period, shares, new issues			84.5
Stockholders' Equity, Other	4
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning balance	(5,763)	(2,950)
Net Income (Loss)	(245)	(448)
Equity Awards Granted, Vested and Exercised	0	0
Balance, ending balance	(6,105)	(3,398)	$ (2,950)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	(97)
Stockholders' Equity, Other	0
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning balance	(1,519)	(1,610)
Other Comprehensive Income	5	43
Equity Awards Granted, Vested and Exercised	0	0
Balance, ending balance	(1,514)	(1,567)	(1,610)
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning balance	55	56
Net Income (Loss)	3	5
Dividends Paid to Noncontrolling Interests	(4)	(5)
Equity Awards Granted, Vested and Exercised	0	0
Balance, ending balance	44	$ 56	$ 56
Stockholders' Equity, Other	$ (10)