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, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Expected tax provision at Swiss statutory rate	$ 880	$ 411	$ 365
Taxes on earnings subject to rates other that Swiss statutory rate	(337)	376	372
Tax exempt interest and dividends received deduction, net of proration	(41)	(49)	(75)
Net witholding taxes	67	40	33
Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-based Payment Arrangement, Amount	(10)	(12)	(19)
Income tax benefit related to 2017 Tax Act	0	0	(25)
Other	70	29	44
Provision for income taxes	$ 629	$ 795	$ 695