Investment Securities (Summary Of Agency Securities Pledged As Collateral Under Repurchase Agreements By Remaining Maturity) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value Of CMO Securities Directly Held	$ 719	$ 426
Fair value	79,935	50,313
Amortized cost	78,003	49,342
Accrued Interest on pledged agency securities	222	161
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	0	101
Available-for-sale Securities Pledged as Collateral	79,966	50,667
Security Owned and Pledged as Collateral, Fair Value	79,935	50,414
All securities pledged collateral at amortized cost	78,003	49,443
30 Days or Less [Member]
Fair value	29,284	19,772
Amortized cost	28,525	19,361
Accrued Interest on pledged agency securities	82	63
Maturity 31 To 59 Days [Member]
Fair value	21,716	16,964
Amortized cost	21,251	16,648
Accrued Interest on pledged agency securities	58	55
Maturity 60 To 90 Days [Member]
Fair value	16,188	8,337
Amortized cost	15,780	8,179
Accrued Interest on pledged agency securities	45	26
Greater than 90 Days [Member]
Fair value	12,747	5,240
Amortized cost	12,447	5,154
Accrued Interest on pledged agency securities	37	17
Treasuries [Member]
Amortized cost	0	101
Repurchase Agreements [Member]
Available-for-sale Securities Pledged as Collateral	78,400	50,255
Repurchase Agreements [Member] | Treasuries [Member]
Available-for-sale Securities Pledged as Collateral	$ 0	$ 101