Investment Securities (Schedule Of Realized Gain (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Abstract]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities	$ 0	$ 0	$ 0
Available-for-sale securities, gross realized gains	82	12	106
Available-for-sale securities, gross realized losses	(4)	(1)	(4)
Net realized gains on available-for-sale securities	78	11	102
Net realized gain on equity securities	73	60
Net unrealized gain (loss) on equity securities	92	(121)
Other gain (loss) on investments, net	$ 243	$ (50)	$ 102