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		3 Months Ended	12 Months Ended
		Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Expected tax provision at Swiss statutory rate			$ 258	$ 273	$ 331
Taxes on earnings subject to rates other that Swiss statutory rate			193	224	124
Income Tax Reconciliation, Change To Deferred Taxes Related To Unrealized Foreign Exchange	[1]		0	139	0
Tax exempt interest and dividends received deduction, net of proration			(32)	(33)	(27)
Net witholding taxes			35	33	27
Change in valuation allowance			2	(20)	4
Other			6	18	21
Provision for income taxes			$ 462	$ 634	$ 480
Income Tax Reconciliation, Change To Deferred Taxes Related to Unrealized Foreign Exchange Net		$ 89

[1] (1) 2014 includes a charge to deferred taxes related to non-recognition of foreign tax credits related to unrealized foreign exchange losses.