Investment Securities (Schedule Of Realized Gain (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Available-for-sale securities, gross realized gains	$ 173	$ 82	$ 12
Available-for-sale securities, gross realized losses	(2)	(4)	(1)
Net realized gains on available-for-sale securities	171	78	11
Net realized gain on equity securities	107	73	60
Net unrealized gain (loss) on equity securities	29	92	(121)
Other gain (loss) on investments, net	$ 307	$ 243	$ (50)