Taxation (Components Of Net Deferred Tax Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred Tax Assets, Gross [Abstract]
Loss reserve discount	$ 826	$ 584
Unearned premium reserve	519	471
Foreign tax credits	247	262
Provision for uncollectible balances	37	37
Loss carry-forwards	143	137
Debt related amounts	74	71
Compensation related amounts	261	263
Cumulative translation adjustments	33	43
Unrealized depreciation on investments	0	102
Deferred Tax Asset, Lease Liability	140	0
Other, net	0	95
Total deferred tax assets	2,280	2,065
Deferred Tax Liabilities, Gross [Abstract]
Deferred policy acquisition costs	588	621
VOBA and other intangible assets	1,468	1,440
Un-remitted foreign earnings	73	47
Investments	40	59
Unrealized appreciation on investments	470	0
Depreciation	157	123
Leasing Arrangements	129	0
Deferred Tax Liabilities, Other	45	0
Deferred Tax Liabilities, Gross	2,970	2,290
Valuation allowance	114	79
Deferred Tax Liabilities, Net	$ (804)	$ (304)