Summary of Significant Commitments (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Commitments to Extend Credit
Long-term Purchase Commitment [Line Items]
Commitments	$ 66,884	$ 63,827
Letters of Credit
Long-term Purchase Commitment [Line Items]
Commitments	3,055	3,974
Forward Contracts Related to Held for Sale Residential Mortgage Loans
Long-term Purchase Commitment [Line Items]
Commitments	1,330	999
Noncancelable Operating Lease Obligations
Long-term Purchase Commitment [Line Items]
Commitments	635	697
Capital Commitments for Private Equity Investments
Long-term Purchase Commitment [Line Items]
Commitments	60	78
Purchase Obligations
Long-term Purchase Commitment [Line Items]
Commitments	60	77
Capital Expenditures
Long-term Purchase Commitment [Line Items]
Commitments	30	28
Capital Lease Obligations
Long-term Purchase Commitment [Line Items]
Commitments	$ 27	$ 37