Income Taxes Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	7.83%	7.83%	7.83%
Swiss Federal Income Tax Rate at 7.83%	$ 208	$ 225	$ 164
Tax on Operating Earnings Subject to Rates Different than the Swiss Federal Income Tax Rate	123	319	411
U.S. Tax Reform - Remeasure of U.S. Deferred Tax Assets	(249)	0	0
Non-cash Tax Expense on Distribution of Subsidiary Earnings	0	137	265
Change in Valuation Allowance Attributed to U.S. Tax Reform	301	0	0
Change in Valuation Allowance	(459)	(872)	(159)
Change in Uncertain Tax Positions	61	31	6
(Provision) Benefit for Income Taxes	$ (137)	$ (496)	$ 145