Reinsurance (Summary Of Net Premiums Earned By Segment) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Net Premiums Earned By Segment [Line Items]
Premiums Earned Net	$ 133,229	$ 117,373	$ 104,109
Commercial and Specialty Business Segment [Member]
Net Premiums Earned By Segment [Line Items]
Premiums Earned Net	35,633	33,209	31,471
Government Business [Member]
Net Premiums Earned By Segment [Line Items]
Premiums Earned Net	96,323	82,520	71,188
Other Segment [Member]
Net Premiums Earned By Segment [Line Items]
Premiums Earned Net	$ 1,273	$ 1,644	$ 1,450