Income Taxes - Components of Income Tax (Benefit) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Current	$ 45	$ 22	$ 194	$ 71
Deferred	14	(115)	(150)	(988)
Total Income Tax Expense (Benefit)	$ 59	$ (93)	$ 44	$ (917)
Effective Tax Rate	19.20%	44.70%	5.10%	36.90%