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
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments not Designated as Hedging Instruments, Gain (Loss) [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ (36)	$ 25
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	(93)	(18)
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	46	(15)
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	2	0
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	9	11
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	(2)	(6)
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	(1)
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	6	5
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	0
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	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	$ (6)	$ 48