Commitments (Summary of Significant Commitments) (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Commitments to extend credit
Long-term Purchase Commitment
Commitments	$ 67,566	$ 66,884
Letters of credit
Long-term Purchase Commitment
Commitments	2,606	3,055
Forward contracts related to residential mortgage loans held for sale
Long-term Purchase Commitment
Commitments	2,033	1,330
Noncancelable operating lease obligations
Long-term Purchase Commitment
Commitments	592	635
Capital commitments for private equity investments
Long-term Purchase Commitment
Commitments	65	60
Purchase obligations
Long-term Purchase Commitment
Commitments	61	60
Capital expenditures
Long-term Purchase Commitment
Commitments	34	30
Capital lease obligations
Long-term Purchase Commitment
Commitments	$ 21	$ 27