Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Assets:
Available-for-sale and other securities, fair value	$ 22,408	[1]	$ 18,597	[1]
Trading securities	360		343
Derivative assets	2,080		1,553
Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	21,808	[2]	17,846	[2]
Trading securities	360		343
Residential mortgage loans held for sale	561		890
Residential mortgage loans	108	[3]	92	[3]
Derivative assets	2,080		1,553
Total assets	24,917		20,724
Liabilities:
Derivative liabilities	1,043		754
Short positions	21		8
Total liabilities	1,064		762
Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	900		827
Liabilities:
Derivative liabilities	284		389
Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets	417		276
Liabilities:
Derivative liabilities	372		252
Equity Contract | Fair value, recurring
Assets:
Derivative assets	415		384
Liabilities:
Derivative liabilities	49		48
Commodity Contract | Fair value, recurring
Assets:
Derivative assets	348		66
Liabilities:
Derivative liabilities	338		65
U.S. Treasury and federal agencies
Assets:
Available-for-sale and other securities, fair value	1,632		1,670
U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	1,632		1,670
Trading securities	14		5
Obligations of states and political subdivisions
Assets:
Available-for-sale and other securities, fair value	192		192
Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	192		192
Trading securities	8		13
Agency mortgage-backed securities | Residential mortgage backed securities
Assets:
Available-for-sale and other securities, fair value	12,404	[4]	12,284	[4]
Agency mortgage-backed securities | Residential mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	12,404		12,284
Trading securities	9		3
Agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member]
Assets:
Available-for-sale and other securities, fair value	4,565
Agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	4,565
Non-agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member]
Assets:
Available-for-sale and other securities, fair value	1,550		1,395
Non-agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	1,550		1,395
Asset-backed securities and other debt securities
Assets:
Available-for-sale and other securities, fair value	1,362		2,187
Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	1,362		2,187
Trading securities	13		7
Equity securities
Assets:
Available-for-sale and other securities, fair value	703	[5]	869	[5]
Equity securities | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	103	[2]	118	[2]
Trading securities	316		315
Fair Value, Inputs, Level 1 | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	109	[2],[6]	115	[2],[6]
Trading securities	316	[6]	316	[6]
Derivative assets	68	[6]	31	[6]
Total assets	493	[6]	462	[6]
Liabilities:
Derivative liabilities	64	[6]	10	[6]
Short positions	16	[6]	4	[6]
Total liabilities	80	[6]	14	[6]
Fair Value, Inputs, Level 1 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets			13	[6]
Liabilities:
Derivative liabilities	6	[6]	1	[6]
Fair Value, Inputs, Level 1 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets	68	[6]	18	[6]
Liabilities:
Derivative liabilities	58	[6]	9	[6]
Fair Value, Inputs, Level 1 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	25	[6]	26	[6]
Trading securities			1	[6]
Fair Value, Inputs, Level 1 | Equity securities | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	84	[2],[6]	89	[2],[6]
Trading securities	316	[6]	315	[6]
Fair Value, Inputs, Level 2 | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	21,699	[2],[6]	17,731	[2],[6]
Trading securities	44	[6]	26	[6]
Residential mortgage loans held for sale	561	[6]	890	[6]
Derivative assets	1,585	[6]	1,126	[6]
Total assets	23,889	[6]	19,773	[6]
Liabilities:
Derivative liabilities	928	[6]	692	[6]
Short positions	5	[6]	4	[6]
Total liabilities	933	[6]	696	[6]
Fair Value, Inputs, Level 2 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	888	[6]	802	[6]
Liabilities:
Derivative liabilities	276	[6]	384	[6]
Fair Value, Inputs, Level 2 | Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets	417	[6]	276	[6]
Liabilities:
Derivative liabilities	372	[6]	252	[6]
Fair Value, Inputs, Level 2 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets	280	[6]	48	[6]
Liabilities:
Derivative liabilities	280	[6]	56	[6]
Fair Value, Inputs, Level 2 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	1,607	[6]	1,644	[6]
Trading securities	14	[6]	4	[6]
Fair Value, Inputs, Level 2 | Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	192	[6]	192	[6]
Trading securities	8	[6]	12	[6]
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Residential mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	12,404	[6]	12,284	[6]
Trading securities	9	[6]	3	[6]
Fair Value, Inputs, Level 2 | Non-agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	1,550	[6]	1,395	[6]
Fair Value, Inputs, Level 2 | Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	1,362	[6]	2,187	[6]
Trading securities	13	[6]	7	[6]
Fair Value, Inputs, Level 2 | Equity securities | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	19	[2],[6]	29	[2],[6]
Fair Value, Inputs, Level 2 | Equity securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value	4,565	[6]
Fair Value, Inputs, Level 3 | Fair value, recurring
Assets:
Trading securities			1
Residential mortgage loans	108	[3]	92	[3]
Derivative assets	427		396
Total assets	535		489
Liabilities:
Derivative liabilities	51		52
Total liabilities	51		52
Fair Value, Inputs, Level 3 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	12		12
Liabilities:
Derivative liabilities	2		4
Fair Value, Inputs, Level 3 | Equity Contract | Fair value, recurring
Assets:
Derivative assets	415		384
Liabilities:
Derivative liabilities	49		48
Fair Value, Inputs, Level 3 | Obligations of states and political subdivisions | Fair value, recurring
Assets:
Trading securities			$ 1

[1] Amortized cost of $21,677 and $18,409 at December 31, 2014 and 2013, respectively.

[2] Excludes FHLB and FRB restricted stock totaling $248 and $352, respectively, at December 31, 2014 and $402 and $349, respectively, at December 31, 2013.

[3] Includes residential mortgage loans originated as held for sale and subsequently transferred to held for investment

[4] Includes interest-only mortgage-backed securities of $175 and $262 as of December 31, 2014 and 2013, respectively, recorded at fair value with fair value changes recorded in securities gains, net and securities gains, net – non-qualifying hedges on mortgage servicing rights in the Consolidated Statements of Income.

[5] Equity securities consist of FHLB and FRB restricted stock holdings of $248 and $352, respectively, at December 31, 2014 and, $402 and $349, respectively, at December 31, 2013, that are carried at cost, and certain mutual fund and equity security holdings.

[6] During the years ended December 31, 2014 and 2013, no assets or liabilities were transferred between Level 1 and Level 2.