Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Assets:
Available for sale securities	$ 20,749	[1]	$ 18,597	[1]
Trading securities	347		343
Residential mortgage loans held for sale	103		92
Fair value, recurring
Assets:
Available for sale securities	20,150		17,846	[2]
Trading securities	347		343
Residential mortgage loans held for sale	649		890
Residential mortgage loans	103	[3]	92	[3]
Derivative assets	1,454		1,553
Total assets	22,703		20,724
Liabilities:
Derivative liabilities	623		754
Short positions	11		8
Total liabilities	634		762
Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	836		827
Liabilities:
Derivative liabilities	348		389
Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets	204		276
Liabilities:
Derivative liabilities	164		252
Equity Contract | Fair value, recurring
Assets:
Derivative assets	348		384
Liabilities:
Derivative liabilities	43		48
Commodity Contract | Fair value, recurring
Assets:
Derivative assets	66		66
Liabilities:
Derivative liabilities	68		65
US Treasury and Government | Fair value, recurring
Assets:
Available for sale securities	26		26
Trading securities			1
US Government Agencies Debt Securities | Fair value, recurring
Assets:
Available for sale securities	1,635		1,644
Trading securities	5		4
US States and Political Subdivisions Debt Securities | Fair value, recurring
Assets:
Available for sale securities	194		192
Trading securities	15		13
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises | Fair value, recurring
Assets:
Available for sale securities	14,185		12,284
Trading securities	3		3
Other Debt Securities | Fair value, recurring
Assets:
Available for sale securities	3,991		3,582
Trading securities	10		7
Other Debt And Equity Securities [Member] | Fair value, recurring
Assets:
Available for sale securities	119	[2]	118	[2]
Trading securities	314		315
Fair Value, Inputs, Level 1 | Fair value, recurring
Assets:
Available for sale securities	111	[4]	115	[2],[4]
Trading securities	314	[4]	316	[4]
Derivative assets	12	[4]	31	[4]
Total assets	437	[4]	462	[4]
Liabilities:
Derivative liabilities	18		10	[4]
Short positions	9		4	[4]
Total liabilities	27		14	[4]
Fair Value, Inputs, Level 1 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	2	[4]	13	[4]
Liabilities:
Derivative liabilities	1		1	[4]
Fair Value, Inputs, Level 1 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets	10	[4]	18	[4]
Liabilities:
Derivative liabilities	17		9	[4]
Fair Value, Inputs, Level 1 | US Treasury and Government | Fair value, recurring
Assets:
Available for sale securities	26	[4]	26	[4]
Trading securities			1	[4]
Fair Value, Inputs, Level 1 | Other Debt And Equity Securities [Member] | Fair value, recurring
Assets:
Available for sale securities	85	[2],[4]	89	[2],[4]
Trading securities	314	[4]	315	[4]
Fair Value, Inputs, Level 2 | Fair value, recurring
Assets:
Available for sale securities	20,039	[4]	17,731	[2],[4]
Trading securities	32	[4]	26	[4]
Residential mortgage loans held for sale	649	[4]	890	[4]
Derivative assets	1,078	[4]	1,126	[4]
Total assets	21,798	[4]	19,773	[4]
Liabilities:
Derivative liabilities	559		692	[4]
Short positions	2		4	[4]
Total liabilities	561		696	[4]
Fair Value, Inputs, Level 2 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	818	[4]	802	[4]
Liabilities:
Derivative liabilities	344		384	[4]
Fair Value, Inputs, Level 2 | Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets	204	[4]	276	[4]
Liabilities:
Derivative liabilities	164		252	[4]
Fair Value, Inputs, Level 2 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets	56	[4]	48	[4]
Liabilities:
Derivative liabilities	51		56	[4]
Fair Value, Inputs, Level 2 | US Government Agencies Debt Securities | Fair value, recurring
Assets:
Available for sale securities	1,635	[4]	1,644	[4]
Trading securities	5	[4]	4	[4]
Fair Value, Inputs, Level 2 | US States and Political Subdivisions Debt Securities | Fair value, recurring
Assets:
Available for sale securities	194	[4]	192	[4]
Trading securities	14	[4]	12	[4]
Fair Value, Inputs, Level 2 | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises | Fair value, recurring
Assets:
Available for sale securities	14,185	[4]	12,284	[4]
Trading securities	3	[4]	3	[4]
Fair Value, Inputs, Level 2 | Other Debt Securities | Fair value, recurring
Assets:
Available for sale securities	3,991	[4]	3,582	[4]
Trading securities	10	[4]	7	[4]
Fair Value, Inputs, Level 2 | Other Debt And Equity Securities [Member] | Fair value, recurring
Assets:
Available for sale securities	34	[2],[4]	29	[2],[4]
Fair Value, Inputs, Level 3 | Fair value, recurring
Assets:
Trading securities	1		1
Residential mortgage loans	103	[3]	92	[3]
Derivative assets	364		396
Total assets	468		489
Liabilities:
Derivative liabilities	46		52
Total liabilities	46		52
Fair Value, Inputs, Level 3 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	16		12
Liabilities:
Derivative liabilities	3		4
Fair Value, Inputs, Level 3 | Equity Contract | Fair value, recurring
Assets:
Derivative assets	348		384
Liabilities:
Derivative liabilities	43		48
Fair Value, Inputs, Level 3 | US States and Political Subdivisions Debt Securities | Fair value, recurring
Assets:
Trading securities	$ 1		$ 1

[1] Amortized cost of $20,393 and $18,409 at March 31, 2014 and December 31, 2013, respectively.

[2] Excludes FHLB and FRB restricted stock totaling $249 and $350, respectively, at March 31, 2014 and $402 and $349 at December 31, 2013, respectively.

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

[4] During the three months ended March 31, 2014 and the year ended December 31, 2013, no assets or liabilities were transferred between Level 1 and Level 2.