Derivative Financial Instruments Derivative Instruments not Designated as Hedging Instruments, Gain (Loss) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments not Designated as Hedging Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 59	$ 69	$ (4)	$ 90
Interest Rate Contract [Member] | Mortgage Servicing Income [Member] | Mortgage Servicing Rights [Member]
Derivative Instruments not Designated as Hedging Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(37)	45	(157)	25
Interest Rate Contract [Member] | Mortgage Production Income [Member] | Loans Held-For-Sale [Member]
Derivative Instruments not Designated as Hedging Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	1	(23)	48	(38)
Interest Rate Contract [Member] | Other Income [Member] | Loans Held-For-Investment [Member]
Derivative Instruments not Designated as Hedging Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	1	(1)	3	(1)
Interest Rate Contract [Member] | Other Trading [Member] | Other Trading [Member]
Derivative Instruments not Designated as Hedging Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	21	12	30	23
Foreign Exchange Contract [Member] | Other Trading [Member] | Other Trading [Member]
Derivative Instruments not Designated as Hedging Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	42	(27)	40	(33)
Credit Risk Contract [Member] | Other Income [Member] | Loans Held-For-Investment [Member]
Derivative Instruments not Designated as Hedging Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(1)	(2)	(1)	(2)
Credit Risk Contract [Member] | Other Trading [Member] | Other Trading [Member]
Derivative Instruments not Designated as Hedging Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	5	7	11	12
Equity Contract [Member] | Other Trading [Member] | Other Trading [Member]
Derivative Instruments not Designated as Hedging Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	1	(1)	2	(1)
Other Contract [Member] | Other Trading [Member] | Commodity Contract [Member]
Derivative Instruments not Designated as Hedging Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	0	0	1
Other Contract [Member] | Mortgage Production and Commercial Real Estate Related Income [Member] | Interest Rate Lock Commitments [Member]
Derivative Instruments not Designated as Hedging Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 26	$ 59	$ 20	$ 104