Investment Securities (Summary Of Agency Securities Pledged As Collateral Under Repurchase Agreements By Remaining Maturity) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair Value Of CMO Securities Directly Held	$ 673	$ 719
Fair value	70,958	79,935
Amortized cost	69,807	78,003
Accrued Interest on pledged agency securities	200	222
Available-for-sale Securities Pledged as Collateral	70,094	79,966
30 Days or Less [Member]
Fair value	28,076	29,284
Amortized cost	27,572	28,525
Accrued Interest on pledged agency securities	80	82
Maturity 31 To 59 Days [Member]
Fair value	14,020	21,716
Amortized cost	13,774	21,251
Accrued Interest on pledged agency securities	39	58
Maturity 60 To 90 Days [Member]
Fair value	7,321	16,188
Amortized cost	7,241	15,780
Accrued Interest on pledged agency securities	21	45
Greater than 90 Days [Member]
Fair value	21,541	12,747
Amortized cost	21,220	12,447
Accrued Interest on pledged agency securities	60	37
Repurchase Agreements [Member]
Available-for-sale Securities Pledged as Collateral	$ 69,537	$ 78,400