Commitments (Summary of Significant Commitments) (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Commitments to extend credit
Long-term Purchase Commitment
Commitments	$ 67,242	$ 67,909
Letters of credit
Long-term Purchase Commitment
Commitments	2,358	2,583
Forward contracts related to residential mortgage loans held for sale
Long-term Purchase Commitment
Commitments	1,749	1,823
Noncancelable operating lease obligations
Long-term Purchase Commitment
Commitments	556	576
Purchase obligations
Long-term Purchase Commitment
Commitments	110	57
Capital commitments for private equity investments
Long-term Purchase Commitment
Commitments	58	59
Capital expenditures
Long-term Purchase Commitment
Commitments	42	29
Capital lease obligations
Long-term Purchase Commitment
Commitments	$ 17	$ 19