Derivative Financial Instruments (Derivative Classifications and Hedging Relationships) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivative financial instruments, notional values	$ 72,321	$ 59,318
Total derivative asset	1,122	864
Amounts subject to master netting arrangements not offset due to policy election, assets column	(629)	(514)
Cash collateral (received) posted	(190)	(44)
Net amount	303	306
Total derivative liability	(1,013)	(970)
Amounts subject to master netting arrangements not offset due to policy election, liabilities column	629	514
Cash collateral (received) posted	342	386
Net amount	(42)	(70)
Cash Flow Hedges [Member] | Interest Rate Contract [Member] | Pay Fixed Swaps [Member] | Three Month LIBOR Funding [Member]
Derivative financial instruments, notional values	9,300	4,300
Total derivative asset	0	0
Total derivative liability	(289)	(203)
Fair Value Hedges [Member] | Interest Rate Contract [Member]
Derivative financial instruments, notional values	12,399	7,345
Total derivative asset	269	102
Total derivative liability	(134)	(89)
Fair Value Hedges [Member] | Interest Rate Contract [Member] | Receive Fixed Swaps [Member] | Long-term Debt [Member]
Derivative financial instruments, notional values	11,902	6,822
Fair value hedge assets	269	102
Fair value hedge liabilities	(5)	(3)
Fair Value Hedges [Member] | Interest Rate Contract [Member] | Pay Fixed Swaps [Member] | Commercial Loans [Member]
Derivative financial instruments, notional values	161	178
Total derivative asset	0	0
Total derivative liability	(3)	(3)
Fair Value Hedges [Member] | Interest Rate Contract [Member] | Pay Fixed Swaps [Member] | Municipal Securities [Member]
Derivative financial instruments, notional values	336	345
Total derivative asset	0	0
Total derivative liability	(126)	(83)
Not Designated as Hedging Instrument [Member]
Derivative financial instruments, notional values	50,622	47,673
Total derivative asset	853	762
Total derivative liability	(590)	(678)
Not Designated as Hedging Instrument [Member] | Client-Related and Other Risk Management [Member]
Derivative financial instruments, notional values	23,955	19,414
Total derivative asset	375	411
Total derivative liability	(404)	(446)
Not Designated as Hedging Instrument [Member] | Client-Related and Other Risk Management [Member] | Interest Rate Contract [Member] | Receive Fixed Swaps [Member]
Derivative financial instruments, notional values	7,995	8,619
Total derivative asset	350	370
Total derivative liability	(3)	(37)
Not Designated as Hedging Instrument [Member] | Client-Related and Other Risk Management [Member] | Interest Rate Contract [Member] | Pay Fixed Swaps [Member]
Derivative financial instruments, notional values	8,163	8,401
Total derivative asset	1	31
Total derivative liability	(375)	(396)
Not Designated as Hedging Instrument [Member] | Client-Related and Other Risk Management [Member] | Interest Rate Contract [Member] | Other Swaps [Member]
Derivative financial instruments, notional values	1,372	1,586
Total derivative asset	5	6
Total derivative liability	(7)	(8)
Not Designated as Hedging Instrument [Member] | Client-Related and Other Risk Management [Member] | Interest Rate Contract [Member] | Other [Member]
Derivative financial instruments, notional values	528	424
Total derivative asset	1	2
Total derivative liability	(1)	(2)
Not Designated as Hedging Instrument [Member] | Client-Related and Other Risk Management [Member] | Forward Commitments [Member]
Derivative financial instruments, notional values	5,326	0
Total derivative asset	10	0
Total derivative liability	(12)	0
Not Designated as Hedging Instrument [Member] | Client-Related and Other Risk Management [Member] | Foreign Exchange Contract [Member]
Derivative financial instruments, notional values	571	384
Total derivative asset	8	2
Total derivative liability	(6)	(3)
Not Designated as Hedging Instrument [Member] | Mortgage Banking [Member] | Interest Rate Contract [Member]
Derivative financial instruments, notional values	5,105	5,500
Total derivative asset	30	45
Total derivative liability	(25)	(28)
Not Designated as Hedging Instrument [Member] | Mortgage Banking [Member] | Interest Rate Contract [Member] | Interest Rate Lock Commitments [Member]
Derivative financial instruments, notional values	1,566	1,869
Total derivative asset	20	3
Total derivative liability	0	(14)
Not Designated as Hedging Instrument [Member] | Mortgage Banking [Member] | Interest Rate Contract [Member] | When Issued Securities And Forward Rate Agreements And Forward Commitments [Member]
Derivative financial instruments, notional values	2,623	3,100
Total derivative asset	3	34
Total derivative liability	(25)	(7)
Not Designated as Hedging Instrument [Member] | Mortgage Banking [Member] | Interest Rate Contract [Member] | Other [Member]
Derivative financial instruments, notional values	916	531
Total derivative asset	7	8
Total derivative liability	0	(7)
Not Designated as Hedging Instrument [Member] | MSRs [Member] | Interest Rate Contract [Member]
Derivative financial instruments, notional values	21,562	22,759
Total derivative asset	448	306
Total derivative liability	(161)	(204)
Not Designated as Hedging Instrument [Member] | MSRs [Member] | Interest Rate Contract [Member] | Receive Fixed Swaps [Member]
Derivative financial instruments, notional values	4,119	6,139
Total derivative asset	215	36
Total derivative liability	(1)	(141)
Not Designated as Hedging Instrument [Member] | MSRs [Member] | Interest Rate Contract [Member] | Pay Fixed Swaps [Member]
Derivative financial instruments, notional values	4,362	5,449
Total derivative asset	1	89
Total derivative liability	(124)	(29)
Not Designated as Hedging Instrument [Member] | MSRs [Member] | Interest Rate Contract [Member] | Option Trades [Member]
Derivative financial instruments, notional values	9,350	9,415
Total derivative asset	229	181
Total derivative liability	(36)	(31)
Not Designated as Hedging Instrument [Member] | MSRs [Member] | Interest Rate Contract [Member] | When Issued Securities And Forward Rate Agreements And Forward Commitments [Member]
Derivative financial instruments, notional values	3,731	1,756
Total derivative asset	3	0
Total derivative liability	$ 0	$ (3)