Fair Value Measurements (Changes In Level 3 Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - Interest rate contracts - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Balance at beginning of period		$ 44	$ 21	$ 22	$ 9
Realized gains (losses) recorded in earnings	[1]	0	1	0	1
Unrealized gains (losses) recorded in earnings	[1]	(2)	7	20	19
Sales		0	(1)	0	(1)
Balance at end of period		$ 42	$ 28	$ 42	$ 28

[1] Realized and unrealized gains and losses due to changes in fair value are recorded in other noninterest income on the Consolidated Statements of Comprehensive Income.