Income Taxes Effective Income Tax Rates (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income tax provision (benefit)	$ 141	$ (107)	$ 216	$ (414)
Effective Income Tax Rate Reconciliation, Percent	31.00%	(34.00%)	37.00%	(37.00%)
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	$ (160)	$ (109)	$ (205)	$ (390)
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	31	(8)	29	(39)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	228	11	361	17
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	0	(2)	(13)	(4)
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	42	1	44	2
Net Income (Loss) Attributable to Parent	$ (599)	$ (192)	$ (5,695)	$ (769)
Effective income tax rate excluding Libya	7.00%	(31.00%)	5.00%	(35.00%)