Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Assets:
Available-for-sale securities, fair value	$ 22,912	[1]	$ 18,597	[1]
Trading securities	389		343
Fair value, recurring
Assets:
Available-for-sale securities, fair value	22,312	[2]	17,846	[2]
Trading securities	389		343
Residential mortgage loans held for sale	579		890
Residential mortgage loans	109	[3]	92	[3]
Derivative assets	1,532		1,553
Total assets	24,921		20,724
Liabilities:
Derivative liabilities	677		754
Short positions	30		8
Total liabilities	707		762
Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	778		827
Liabilities:
Derivative liabilities	286		389
Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets	313		276
Liabilities:
Derivative liabilities	258		252
Equity Contract | Fair value, recurring
Assets:
Derivative assets	358		384
Liabilities:
Derivative liabilities	53		48
Commodity Contract | Fair value, recurring
Assets:
Derivative assets	83		66
Liabilities:
Derivative liabilities	80		65
U.S. Treasury and federal agencies
Assets:
Available-for-sale securities, fair value	1,739		1,670
U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale securities, fair value	1,739		1,670
Trading securities	14		5
Obligations of states and political subdivisions
Assets:
Available-for-sale securities, fair value	193		192
Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale securities, fair value	193		192
Trading securities	32		13
Agency mortgage-backed securities | Residential mortgage backed securities
Assets:
Available-for-sale securities, fair value	13,060	[4]	12,284	[4]
Agency mortgage-backed securities | Residential mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value	13,060		12,284
Trading securities	9		3
Agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member]
Assets:
Available-for-sale securities, fair value	4,255
Agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale securities, fair value	4,255
Non-agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member]
Assets:
Available-for-sale securities, fair value	1,569		1,395
Non-agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale securities, fair value	1,569		1,395
Asset-backed securities and other debt securities
Assets:
Available-for-sale securities, fair value	1,370		2,187
Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value	1,370		2,187
Trading securities	19		7
Equity securities
Assets:
Available-for-sale securities, fair value	726	[5]	869	[5]
Equity securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value	126	[2]	118	[2]
Trading securities	315		315
Fair Value, Inputs, Level 1 | Fair value, recurring
Assets:
Available-for-sale securities, fair value	207	[2],[6]	115	[2],[6]
Trading securities	315	[6]	316	[6]
Derivative assets	13	[6]	31	[6]
Total assets	535	[6]	462	[6]
Liabilities:
Derivative liabilities	10	[6]	10	[6]
Short positions	26	[6]	4	[6]
Total liabilities	36	[6]	14	[6]
Fair Value, Inputs, Level 1 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	1	[6]	13	[6]
Liabilities:
Derivative liabilities	2	[6]	1	[6]
Fair Value, Inputs, Level 1 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets	12	[6]	18	[6]
Liabilities:
Derivative liabilities	8	[6]	9	[6]
Fair Value, Inputs, Level 1 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale securities, fair value	123	[6]	26	[6]
Trading securities			1	[6]
Fair Value, Inputs, Level 1 | Equity securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value	84	[2],[6]	89	[2],[6]
Trading securities	315	[6]	315	[6]
Fair Value, Inputs, Level 2 | Fair value, recurring
Assets:
Available-for-sale securities, fair value	22,105	[2],[6]	17,731	[2],[6]
Trading securities	73	[6]	26	[6]
Residential mortgage loans held for sale	579	[6]	890	[6]
Derivative assets	1,151	[6]	1,126	[6]
Total assets	23,908	[6]	19,773	[6]
Liabilities:
Derivative liabilities	611	[6]	692	[6]
Short positions	4	[6]	4	[6]
Total liabilities	615	[6]	696	[6]
Fair Value, Inputs, Level 2 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	767	[6]	802	[6]
Liabilities:
Derivative liabilities	281	[6]	384	[6]
Fair Value, Inputs, Level 2 | Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets	313	[6]	276	[6]
Liabilities:
Derivative liabilities	258	[6]	252	[6]
Fair Value, Inputs, Level 2 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets	71	[6]	48	[6]
Liabilities:
Derivative liabilities	72	[6]	56	[6]
Fair Value, Inputs, Level 2 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale securities, fair value	1,616	[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 securities, fair value	193	[6]	192	[6]
Trading securities	31	[6]	12	[6]
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Residential mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value	13,060	[6]	12,284	[6]
Trading securities	9	[6]	3	[6]
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale securities, fair value	4,255	[6]
Fair Value, Inputs, Level 2 | Non-agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale securities, fair value	1,569	[6]	1,395	[6]
Fair Value, Inputs, Level 2 | Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value	1,370	[6]	2,187	[6]
Trading securities	19	[6]	7	[6]
Fair Value, Inputs, Level 2 | Equity securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value	42	[2],[6]	29	[2],[6]
Fair Value, Inputs, Level 3 | Fair value, recurring
Assets:
Trading securities	1		1
Residential mortgage loans	109	[3]	92	[3]
Derivative assets	368		396
Total assets	478		489
Liabilities:
Derivative liabilities	56		52
Total liabilities	56		52
Fair Value, Inputs, Level 3 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	10		12
Liabilities:
Derivative liabilities	3		4
Fair Value, Inputs, Level 3 | Equity Contract | Fair value, recurring
Assets:
Derivative assets	358		384
Liabilities:
Derivative liabilities	53		48
Fair Value, Inputs, Level 3 | Obligations of states and political subdivisions | Fair value, recurring
Assets:
Trading securities	$ 1		$ 1

[1] Amortized cost of $22,392 and $18,409 at September 30, 2014 and December 31, 2013, respectively.

[2] Excludes FHLB and FRB restricted stock totaling $249 and $351, respectively, at September 30, 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 $192 and $262 as of September 30, 2014 and December 31, 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 Condensed Consolidated Statements of Income.

[5] Equity securities consist of FHLB and FRB restricted stock holdings of $249 and $351, respectively, at September 30, 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 three and nine months ended September 30, 2014 and for the year ended December 31, 2013, no assets or liabilities were transferred between Level 1 and Level 2.