Fair Value Measurements (Changes In Level 3 Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Change in classification		$ 0	$ 81
Interest rate contracts
Balance at beginning of period		9	14
Change in classification		0	0
Realized gains (losses) recorded in earnings	[1]	0	0
Unrealized gains (losses) recorded in earnings	[1]	5	(7)
Sales and redemptions		0	0
Balance at end of period		$ 14	7
Investment Securities Available-For-Sale
Balance at beginning of period			49
Change in classification	[2]		(44)
Realized gains (losses) recorded in earnings	[1]		0
Unrealized gains (losses) recorded in earnings	[1]		0
Sales and redemptions			5
Balance at end of period			0
Equity and other non-debt securities | Equity and other non-debt securities
Balance at beginning of period			0
Change in classification	[2]		44
Realized gains (losses) recorded in earnings	[1]		0
Unrealized gains (losses) recorded in earnings	[1]		0
Sales and redemptions			(44)
Balance at end of period			0
Equity and other non-debt securities | Investment Securities Available-For-Sale
Balance at beginning of period	[3]		44
Change in classification	[2],[3]		(44)
Realized gains (losses) recorded in earnings	[1],[3]		0
Unrealized gains (losses) recorded in earnings	[1],[3]		0
Sales and redemptions	[3]		0
Balance at end of period	[3]		0
State and municipal securities | Investment Securities Available-For-Sale
Balance at beginning of period	[3]		5
Change in classification	[3]		0
Realized gains (losses) recorded in earnings	[1],[3]		0
Unrealized gains (losses) recorded in earnings	[1],[3]		0
Sales and redemptions	[3]		(5)
Balance at end of period	[3]		$ 0

[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.

[2] Reflects the reclassification of equity securities resulting from the adoption of ASU 2016-01.

[3] Auction-rate securities.