Financial Derivatives (Gains (Losses) on Derivatives Not Designated As Hedging Instruments under GAAP) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	$ 167	$ 329
Residential Mortgages [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	188	119
Residential Mortgages [Member] | Residential Mortgage Servicing Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	195	98
Residential Mortgages [Member] | Loan Sales Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	(7)	21
Commercial Mortgage Banking [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	53	29
Commercial Mortgage Banking [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	53	30
Commercial Mortgage Banking [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net		(1)
Customer Contracts [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	25	5
Customer Contracts [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	(4)	4
Customer Contracts [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	29	1
Other Risk Management Activity [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	(99)	176
Other Risk Management Activity [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	(95)	183
Other Risk Management Activity [Member] | Other Contract [Member]
Derivative [Line Items]
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net	$ (4)	$ (7)