Shareholders' Equity (Shareholders' Equity Activity) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning balance	$ (3,666)	$ (571)
Net Income (Loss)	(477)	(242)
Other Comprehensive Income	33	5
Dividends Paid to Noncontrolling Interests	(5)	(4)
Equity Awards Granted, Vested and Exercised	8	17
Balance, ending balance	(4,106)	(898)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets		(97)
Stockholders' Equity, Other	1	(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
Capital in Excess of Par Value
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning balance	6,711	6,655
Equity Awards Granted, Vested and Exercised	8	17
Balance, ending balance	6,719	6,676
Stockholders' Equity, Other	0	4
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning balance	(8,671)	(5,763)
Net Income (Loss)	(481)	(245)
Equity Awards Granted, Vested and Exercised	0	0
Balance, ending balance	(9,152)	(6,105)
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	(1,746)	(1,519)
Other Comprehensive Income	33	5
Equity Awards Granted, Vested and Exercised	0	0
Balance, ending balance	(1,713)	(1,514)
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning balance	39	55
Net Income (Loss)	4	3
Dividends Paid to Noncontrolling Interests	(5)	(4)
Equity Awards Granted, Vested and Exercised	0	0
Balance, ending balance	39	$ 44
Stockholders' Equity, Other	$ 1		$ (10)