Capital Ratios (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Common Equity Tier 1	$ 16,953	$ 16,421
Common Equity Tier 1 to Risk Weighted Assets	9.59%	9.96%
Tier 1 capital	$ 18,186	$ 17,804
Total capital	$ 21,685	$ 20,668
Tier 1 capital	10.28%	10.80%
Total capital	12.26%	12.54%
Tier One Leverage Capital to Average Assets	9.22%	9.69%
Bank Subsidiaries [Member]
Common Equity Tier 1	$ 18,535	$ 17,859
Common Equity Tier 1 to Risk Weighted Assets	10.71%	11.02%
Tier 1 capital	$ 18,573	$ 17,908
Total capital	$ 21,276	$ 20,101
Tier 1 capital	10.73%	11.05%
Total capital	12.29%	12.40%
Tier One Leverage Capital to Average Assets	9.63%	9.96%
Junior Subordinated Debt [Member] | Parent Company [Member]
Long-term Debt, Percentage Bearing Variable Interest, Amount	$ 627	$ 627
Long-term Debt [Member] | Junior Subordinated Debt [Member] | Parent Company [Member]
Long-term Debt, Percentage Bearing Variable Interest, Amount	$ 627