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		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Balance at beginning of period		$ 22	$ 9
Realized gains (losses) recorded in earnings	[1]	0	1
Unrealized gains (losses) recorded in earnings	[1]	17	13
Sales		0	(1)
Balance at end of period		$ 39	$ 22

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