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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments not Designated as Hedging Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 9	$ 53	$ 5	$ 143
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	(54)	17	(210)	41
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	10	(20)	57	(57)
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	0	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	18	11	48	33
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	9	(10)	49	(43)
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	(5)	(1)	(5)	(3)
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	8	16	19
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	6	(1)	8	(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	$ 19	$ 49	$ 39	$ 154