Summary of Significant Commitments (Detail) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Commitments to extend credit
Long-term Purchase Commitment [Line Items]
Commitments	$ 65,455	$ 63,827
Letters of credit
Long-term Purchase Commitment [Line Items]
Commitments	3,542	3,974
Forward contracts related to held for sale mortgage loans
Long-term Purchase Commitment [Line Items]
Commitments	1,096	999
Noncancelable operating lease obligations
Long-term Purchase Commitment [Line Items]
Commitments	655	697
Purchase obligations
Long-term Purchase Commitment [Line Items]
Commitments	75	77
Capital commitments for private equity funds
Long-term Purchase Commitment [Line Items]
Commitments	66	78
Capital expenditures
Long-term Purchase Commitment [Line Items]
Commitments	38	37
Capital lease obligations
Long-term Purchase Commitment [Line Items]
Commitments	$ 27	$ 28