Summary of Significant Commitments (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Commitments to extend credit
Long-term Purchase Commitment [Line Items]
Commitments	$ 64,425	$ 63,827
Letters of credit
Long-term Purchase Commitment [Line Items]
Commitments	3,781	3,974
Forward contracts related to held for sale mortgage loans
Long-term Purchase Commitment [Line Items]
Commitments	1,956	999
Noncancelable operating lease obligations
Long-term Purchase Commitment [Line Items]
Commitments	693	697
Purchase obligations
Long-term Purchase Commitment [Line Items]
Commitments	71	77
Capital commitments for private equity funds
Long-term Purchase Commitment [Line Items]
Commitments	68	78
Capital expenditures
Long-term Purchase Commitment [Line Items]
Commitments	37	37
Capital lease obligations
Long-term Purchase Commitment [Line Items]
Commitments	$ 30	$ 28