Investment Securities (Schedule Of Realized Gain (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Available-for-sale securities, gross realized gains	$ 45	$ 30	$ 169	$ 64
Available-for-sale securities, gross realized losses	(2)	(3)	(2)	(4)
Net realized gains on available-for-sale securities	43	27	167	60
Net realized gain on equity securities	7	12	88	51
Net unrealized gain (loss) on equity securities	14	(12)	(82)	63
Other gain on investments, net	$ 64	$ 27	$ 173	$ 174