Taxation (Components Of Net Deferred Tax Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets, Gross [Abstract]
Loss reserve discount	$ 715	$ 1,269
Unearned premium reserve	231	498
Foreign tax credits	340	2,115
Provision for uncollectible balances	45	72
Loss carry-forwards	90	92
Debt related amounts	77	219
Compensation related amounts	260	449
Cumulative translation adjustments	30	59
Other, net	70	69
Total deferred tax assets	1,858	4,842
Deferred Tax Liabilities, Gross [Abstract]
Deferred policy acquisition costs	635	842
VOBA and other intangible assets	1,437	2,352
Un-remitted foreign earnings	66	2,001
Investments	53	406
Unrealized appreciation on investments	184	60
Depreciation	83	91
Deferred Tax Liabilities, Gross	2,458	5,752
Valuation allowance	99	78
Deferred Tax Liabilities, Net	$ (699)	$ (988)