Financial Derivatives (Gains (Losses) on Derivatives and Related Hedged Items - Fair Value Hedges) (Details) - Fair Value Hedging [Member] - Designated as Hedging Instrument [Member] - Interest Rate Contracts [Member] - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives Recognized in Income	$ (200,000,000)	$ 46,000,000	$ (95,000,000)	$ 49,000,000
Gain (Loss) on Related Hedged Items Recognized in Income	193,000,000	(56,000,000)	75,000,000	(64,000,000)
The ineffective portion of the change in value of our fair value hedge derivatives	(7,000,000)	(10,000,000)	(20,000,000)	(15,000,000)
US Treasury and Government Agencies Securities [Member] | Investment Securities Interest Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives Recognized in Income	63,000,000	(53,000,000)	12,000,000	(83,000,000)
Gain (Loss) on Related Hedged Items Recognized in Income	(65,000,000)	55,000,000	(12,000,000)	86,000,000
Other Debt Securities [Member] | Investment Securities Interest Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives Recognized in Income	1,000,000	(2,000,000)		(1,000,000)
Gain (Loss) on Related Hedged Items Recognized in Income	(1,000,000)	1,000,000		1,000,000
Subordinated Debts [Member] | Borrowed Funds Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives Recognized in Income	(138,000,000)	51,000,000	(84,000,000)	74,000,000
Gain (Loss) on Related Hedged Items Recognized in Income	130,000,000	(60,000,000)	67,000,000	(89,000,000)
Bank Notes And Senior Debt [Member] | Borrowed Funds Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives Recognized in Income	(126,000,000)	50,000,000	(23,000,000)	59,000,000
Gain (Loss) on Related Hedged Items Recognized in Income	$ 129,000,000	$ (52,000,000)	$ 20,000,000	$ (62,000,000)