Summary of Significant Commitments (Detail) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Commitments to extend credit
Long-term Purchase Commitment [Line Items]
Commitments	$ 66,908	$ 66,884
Letters of credit
Long-term Purchase Commitment [Line Items]
Commitments	2,945	3,055
Forward contracts related to held for sale residential mortgage loans
Long-term Purchase Commitment [Line Items]
Commitments	1,423	1,330
Noncancelable operating lease obligations
Long-term Purchase Commitment [Line Items]
Commitments	618	635
Purchase obligations
Long-term Purchase Commitment [Line Items]
Commitments	70	60
Capital commitments for private equity funds
Long-term Purchase Commitment [Line Items]
Commitments	62	60
Capital expenditures
Long-term Purchase Commitment [Line Items]
Commitments	30	30
Capital lease obligations
Long-term Purchase Commitment [Line Items]
Commitments	$ 24	$ 27