Fair Value Measurements (Changes In Level 3 Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018	Jan. 01, 2018
Interest rate contracts
Balance at beginning of period		$ 9		$ 14
Realized gains (losses) recorded in earnings		1	[1]	0
Unrealized gains (losses) recorded in earnings	[1]	13		(5)
Sales and redemptions		(1)		0
Balance at end of period		22		9
Investment securities available-for-sale
Balance at beginning of period		0		49
Change in classification	[2]				$ (44)
Realized gains (losses) recorded in earnings				0
Unrealized gains (losses) recorded in earnings				0
Sales and redemptions				(5)
Balance at end of period				0
Equity and other non-debt securities | Equity and other non-debt securities
Change in classification	[2]				44
Sales and redemptions				(44)
Equity and other non-debt securities | Investment securities available-for-sale
Balance at beginning of period	[2]	0		44
Change in classification	[2]				$ (44)
Realized gains (losses) recorded in earnings	[2]			0
Unrealized gains (losses) recorded in earnings	[2]			0
Sales and redemptions	[2]			0
Balance at end of period	[2]			0
State and municipal securities | Investment securities available-for-sale
Balance at beginning of period	[2]	$ 0		5
Realized gains (losses) recorded in earnings	[2]			0
Unrealized gains (losses) recorded in earnings	[2]			0
Sales and redemptions	[2]			(5)
Balance at end of period	[2]			$ 0

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

[2] Auction-rate securities.