Income Taxes - Components of Income Tax (Benefit) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Current	$ 23	$ 37	$ 149	$ 49
Deferred	(7)	(873)	(164)	(873)
Total Income Tax Expense (Benefit)	$ (16)	$ 836	$ 15	$ 824
Effective Tax Rate	160.00%	35.80%	(2.70%)	36.20%

Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration