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, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Expected tax provision at Swiss statutory rate	$ 411	$ 365	$ 291
Taxes on earnings subject to rates other that Swiss statutory rate	376	372	263
Tax exempt interest and dividends received deduction, net of proration	(49)	(75)	(199)
Net witholding taxes	40	33	30
Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-based Payment Arrangement, Amount	(12)	(19)	(48)
Income tax benefit related to 2017 Tax Act	0	(25)	(450)
Income Tax Reconciliation, Corporate Owned Life Insurance	(13)	2	(37)
Other	42	42	11
Provision for income taxes	$ 795	$ 695	$ (139)