Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Assets:
Available-for-sale securities, fair value	$ 26,409	[1]	$ 22,408	[1]
Trading securities	392		360
Fair value, recurring
Assets:
Available-for-sale securities, fair value	25,809	[2]	21,808	[2]
Trading securities	392		360
Residential mortgage loans held for sale	689		561
Residential mortgage loans measured at FV	126	[3]	108	[3]
Derivative assets	2,493		2,080
Total assets	29,509		24,917
Liabilities:
Derivative liabilities	1,251		1,043
Short positions	23		21
Total liabilities	1,274		1,064
Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	1,088		900
Liabilities:
Derivative liabilities	332		284
Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets	597		417
Liabilities:
Derivative liabilities	553		372
Equity Contract | Fair value, recurring
Assets:
Derivative assets	485		415
Liabilities:
Derivative liabilities	60		49
Commodity Contract | Fair value, recurring
Assets:
Derivative assets	323		348
Liabilities:
Derivative liabilities	306		338
U.S. Treasury and federal agencies
Assets:
Available-for-sale securities, fair value	1,627		1,632
U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale securities, fair value	1,627		1,632
Trading securities	19		14
Obligations of states and political subdivisions
Assets:
Available-for-sale securities, fair value	192		192
Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale securities, fair value	192		192
Trading securities	55		8
Agency mortgage-backed securities | Residential mortgage backed securities
Assets:
Available-for-sale securities, fair value	15,025	[4]	12,404	[4]
Agency mortgage-backed securities | Residential mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value	15,025		12,404
Trading securities	4		9
Agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member]
Assets:
Available-for-sale securities, fair value	5,447		4,565
Agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale securities, fair value	5,447		4,565
Non-agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member]
Assets:
Available-for-sale securities, fair value	2,014		1,550
Non-agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale securities, fair value	2,014		1,550
Asset-backed securities and other debt securities
Assets:
Available-for-sale securities, fair value	1,402		1,362
Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value	1,402		1,362
Trading securities	15		13
Equity securities
Assets:
Available-for-sale securities, fair value	702	[5]	703	[5]
Equity securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value	102	[2]	103	[2]
Trading securities	299		316
Fair Value, Inputs, Level 1 | Fair value, recurring
Assets:
Available-for-sale securities, fair value	108	[2],[6]	109	[2],[6]
Trading securities	299	[6]	316	[6]
Derivative assets	60	[6]	68	[6]
Total assets	467	[6]	493	[6]
Liabilities:
Derivative liabilities	45	[6]	64	[6]
Short positions	21	[6]	16	[6]
Total liabilities	66	[6]	80	[6]
Fair Value, Inputs, Level 1 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	2	[6]
Liabilities:
Derivative liabilities	7	[6]	6	[6]
Fair Value, Inputs, Level 1 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets	58	[6]	68	[6]
Liabilities:
Derivative liabilities	38	[6]	58	[6]
Fair Value, Inputs, Level 1 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale securities, fair value	25	[6]	25	[6]
Fair Value, Inputs, Level 1 | Equity securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value	83	[2],[6]	84	[2],[6]
Trading securities	299	[6]	316	[6]
Fair Value, Inputs, Level 2 | Fair value, recurring
Assets:
Available-for-sale securities, fair value	25,701	[2],[6]	21,699	[2],[6]
Trading securities	93	[6]	44	[6]
Residential mortgage loans held for sale	689	[6]	561	[6]
Derivative assets	1,929	[6]	1,585	[6]
Total assets	28,412	[6]	23,889	[6]
Liabilities:
Derivative liabilities	1,144	[6]	928	[6]
Short positions	2	[6]	5	[6]
Total liabilities	1,146	[6]	933	[6]
Fair Value, Inputs, Level 2 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	1,067	[6]	888	[6]
Liabilities:
Derivative liabilities	323	[6]	276	[6]
Fair Value, Inputs, Level 2 | Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets	597	[6]	417	[6]
Liabilities:
Derivative liabilities	553	[6]	372	[6]
Fair Value, Inputs, Level 2 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets	265	[6]	280	[6]
Liabilities:
Derivative liabilities	268	[6]	280	[6]
Fair Value, Inputs, Level 2 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale securities, fair value	1,602	[6]	1,607	[6]
Trading securities	19	[6]	14	[6]
Fair Value, Inputs, Level 2 | Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale securities, fair value	192	[6]	192	[6]
Trading securities	55	[6]	8	[6]
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Residential mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value	15,025	[6]	12,404	[6]
Trading securities	4	[6]	9	[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	5,447	[6]	4,565	[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	2,014	[6]	1,550	[6]
Fair Value, Inputs, Level 2 | Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value	1,402	[6]	1,362	[6]
Trading securities	15	[6]	13	[6]
Fair Value, Inputs, Level 2 | Equity securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value	19	[2],[6]	19	[2],[6]
Fair Value, Inputs, Level 3 | Fair value, recurring
Assets:
Residential mortgage loans measured at FV	126	[3]	108	[3]
Derivative assets	504		427
Total assets	630		535
Liabilities:
Derivative liabilities	62		51
Total liabilities	62		51
Fair Value, Inputs, Level 3 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	19		12
Liabilities:
Derivative liabilities	2		2
Fair Value, Inputs, Level 3 | Equity Contract | Fair value, recurring
Assets:
Derivative assets	485		415
Liabilities:
Derivative liabilities	$ 60		$ 49

[1] Amortized cost of $25,475 and $21,677 at March 31, 2015 and December 31, 2014, respectively.

[2] Excludes FHLB and FRB restricted stock totaling $248 and $352, respectively, at March 31, 2015 and December 31, 2014.

[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 $158 and $175 as of March 31, 2015 and December 31, 2014, respectively, recorded at fair value with fair value changes recorded in securities gains, net, in the Condensed Consolidated Statements of Income.

[5] Equity securities consist of FHLB and FRB restricted stock holdings of $248 and $352, respectively, at March 31, 2015 and December 31, 2014, that are carried at cost, and certain mutual fund and equity security holdings.

[6] During the three months ended March 31, 2015 and the year ended December 31, 2014, no assets or liabilities were transferred between Level 1 and Level 2.