Taxation (Reconciliation Of The Difference Between The Provision for Income Taxes and the Expected Tax Provision at Swiss Statutory Income Tax Rate) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Expected tax provision at Swiss statutory rate	$ 365	$ 291	$ 388
Taxes on earnings subject to rates other that Swiss statutory rate	372	263	582
Tax exempt interest and dividends received deduction, net of proration	(75)	(199)	(200)
Net witholding taxes	33	30	20
Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount	(19)	(48)	0
Income tax benefit related to 2017 Tax Act	(25)	(450)	0
Income Tax Reconciliation, Corporate Owned Life Insurance	2	(37)	0
Other	42	11	25
Provision for income taxes	$ 695	$ (139)	$ 815