Capital Ratios (Detail) - USD ($) $ in Millions		Dec. 31, 2015		Dec. 31, 2014
Common Equity Tier 1	[1]	$ 16,421
Common Equity Tier 1 to Risk Weighted Assets	[1]	9.96%
Tier 1 common				$ 15,594
Tier 1 capital		$ 17,804	[1]	17,554
Total capital		$ 20,668	[1]	$ 20,338
Tier 1 common				9.60%
Total capital		12.54%	[1]	12.51%
Tier 1 leverage		9.69%	[1]	9.64%
Excess Tier One Risk Based Capital to Risk Weighted Assets		10.80%	[1]	10.80%
Bank Subsidiaries [Member]
Common Equity Tier 1	[1]	$ 17,859
Common Equity Tier 1 to Risk Weighted Assets	[1]	11.02%
Tier 1 capital		$ 17,908	[1]	$ 17,036
Total capital		$ 20,101	[1]	$ 19,619
Total capital		12.40%	[1]	12.29%
Tier 1 leverage		9.96%	[1]	9.57%
Excess Tier One Risk Based Capital to Risk Weighted Assets		11.05%	[1]	10.67%
Junior Subordinated Debt [Member] | Parent Company [Member]
Long-term Debt, Percentage Bearing Variable Interest, Amount				$ 627
Long-term Debt [Member] | Junior Subordinated Debt [Member] | Parent Company [Member]
Long-term Debt, Percentage Bearing Variable Interest, Amount		$ 627

[1] Basel III Final Rules became effective on January 1, 2015; thus, CET1 is not applicable ("N/A") in periods ending prior to January 1, 2015 and Basel I Tier 1 common equity is N/A in periods ending after January 1, 2015. Tier 1 capital, Total capital, and Leverage ratio for periods ended prior to January 1, 2015 were calculated under Basel I.