Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Income tax expense (benefit) allocated directly to equity	$ (2)	$ (37)	$ (85)
Unrecognized tax benefits that would impact effective tax rate	180
Cash outflow from unrecognized tax benefit that would impact effective tax rate	186
Interest (income) expense recognized related to unrecognized tax benefits	(1)	11	2
Accrued interest related to unrecognized tax benefits	$ 27	$ 28	$ 17
Minimum
Income Taxes [Line Items]
Statue of limitations on foreign jurisdictions for tax audits	3 years
Maximum
Income Taxes [Line Items]
Statue of limitations on foreign jurisdictions for tax audits	6 years