Derivatives and Hedging Activities (Schedule of Impact of the Derivative Instruments on Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Amounts reclassified from OCI into earnings, cash flow hedges	$ (2)	$ 3
Interest Expense [Member] | Deposits [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded	(373)	(386)
Interest Expense [Member] | Deposits [Member] | Designated as Hedges [Member] | Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amounts reclassified from OCI into earnings, cash flow hedges	(1)	1
Gains (losses) on hedged items, fair value hedges	0	0
Gains (losses) on interest rate swaps, fair value hedges	0	0
Total gains (losses) on fair value hedges	0	0
Interest Expense [Member] | Deposits [Member] | Not Designated as Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as hedges	0
Interest Expense [Member] | Long-term Borrowings [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded	(211)	(246)
Interest Expense [Member] | Long-term Borrowings [Member] | Designated as Hedges [Member] | Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amounts reclassified from OCI into earnings, cash flow hedges	(1)	2
Gains (losses) on hedged items, fair value hedges	(396)	(55)
Gains (losses) on interest rate swaps, fair value hedges	405	42
Total gains (losses) on fair value hedges	9	(13)
Interest Expense [Member] | Long-term Borrowings [Member] | Not Designated as Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as hedges	0
Other Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded	28	28
Other Income [Member] | Designated as Hedges [Member] | Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amounts reclassified from OCI into earnings, cash flow hedges	0	0
Gains (losses) on hedged items, fair value hedges	0	0
Gains (losses) on interest rate swaps, fair value hedges	0	0
Total gains (losses) on fair value hedges	0	$ 0
Other Income [Member] | Not Designated as Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as hedges	$ 1