Short-Term Borrowings (Summary Of Short-Term Borrowings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Federal Home Loan Bank Certificates and Obligations (FHLB) [Member]
Short-term Debt [Line Items]
Average amount outstanding	$ 2,971	$ 2,657	$ 37
Weighted average rate	2.01%	1.13%	0.59%
Highest month-end balance	$ 5,400	$ 3,750	$ 750
Year-end balance	$ 4,500	$ 3,600	$ 500
Weighted average rate on outstandings at year-end	2.61%	1.44%	0.75%
Short-term Debt [Member]
Short-term Debt [Line Items]
Year-end balance	$ 5,653	$ 4,976	$ 827
Security Owned and Sold, Not yet Purchased Fair Value, Security Sold, Not yet Purchased	85	95	25
Federal Funds Purchased [Member]
Short-term Debt [Line Items]
Year-end balance	541	927	106
Security Repurchase Agreements [Member]
Short-term Debt [Line Items]
Year-end balance	$ 527	$ 354	$ 196