Summary of Significant Commitments (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Commitments to extend credit
Long-term Purchase Commitment [Line Items]
Commitments	$ 66,661	$ 63,827
Letters of credit
Long-term Purchase Commitment [Line Items]
Commitments	3,323	3,974
Forward contracts related to held for sale residential mortgage loans
Long-term Purchase Commitment [Line Items]
Commitments	1,392	999
Noncancelable operating lease obligations
Long-term Purchase Commitment [Line Items]
Commitments	642	697
Purchase obligations
Long-term Purchase Commitment [Line Items]
Commitments	70	77
Capital commitments for private equity funds
Long-term Purchase Commitment [Line Items]
Commitments	60	78
Capital expenditures
Long-term Purchase Commitment [Line Items]
Commitments	42	28
Capital lease obligations
Long-term Purchase Commitment [Line Items]
Commitments	$ 25	$ 37