Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Millions		Dec. 31, 2015		Dec. 31, 2014
Assets:
Available-for-sale and other securities, fair value	[1]	$ 29,044		$ 22,408
Trading securities		386		360
Residential mortgage loans measured at fair value		167		108
Derivative assets		1,852		2,080
Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		28,440	[2]	21,808	[3]
Trading securities		386		360
Residential mortgage loans held for sale		519		561
Residential mortgage loans measured at fair value		167	[4]	108	[5]
Derivative assets		1,852	[6]	2,080	[7]
Total assets		31,364		24,917
Liabilities:
Derivative liabilities		938	[8]	1,043	[9]
Short positions		29	[8]	21	[9]
Total liabilities		967		1,064
Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		910		900
Liabilities:
Derivative liabilities		261		284
Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets		386		417
Liabilities:
Derivative liabilities		340		372
Equity Contract | Fair value, recurring
Assets:
Derivative assets		262		415
Liabilities:
Derivative liabilities		61		49
Commodity Contract | Fair value, recurring
Assets:
Derivative assets		294		348
Liabilities:
Derivative liabilities		276		338
U.S. Treasury and federal agencies
Assets:
Available-for-sale and other securities, fair value		1,187		1,632
U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		1,187		1,632
Trading securities		19		14
Obligations of states and political subdivisions
Assets:
Available-for-sale and other securities, fair value		52		192
Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		52		192
Trading securities		9		8
Agency mortgage-backed securities | Residential mortgage backed securities
Assets:
Available-for-sale and other securities, fair value	[10]	15,081		12,404
Agency mortgage-backed securities | Residential mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		15,081		12,404
Trading securities		6		9
Agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member]
Assets:
Available-for-sale and other securities, fair value		7,862		4,565
Agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		7,862		4,565
Non-agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member]
Assets:
Available-for-sale and other securities, fair value		2,804		1,550
Non-agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		2,804		1,550
Asset-backed securities and other debt securities
Assets:
Available-for-sale and other securities, fair value		1,355		1,362
Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		1,355		1,362
Trading securities		19		13
Equity securities
Assets:
Available-for-sale and other securities, fair value	[11]	703		703
Equity securities | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		99	[2]	103	[3]
Trading securities		333		316
Fair Value, Inputs, Level 1 | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		198	[2],[12]	109	[3],[13]
Trading securities		333	[12]	316	[13]
Derivative assets		57	[6],[12]	68	[7],[13]
Total assets		588	[12]	493	[13]
Liabilities:
Derivative liabilities		38	[8],[12]	64	[9],[13]
Short positions		22	[8],[12]	16	[9],[13]
Total liabilities		60	[12]	80	[13]
Fair Value, Inputs, Level 1 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets	[12]	3
Liabilities:
Derivative liabilities		1	[12]	6	[13]
Fair Value, Inputs, Level 1 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets		54	[12]	68	[13]
Liabilities:
Derivative liabilities		37	[12]	58	[13]
Fair Value, Inputs, Level 1 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		100	[12]	25	[13]
Fair Value, Inputs, Level 1 | Equity securities | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		98	[2],[12]	84	[3],[13]
Trading securities		333	[12]	316	[13]
Fair Value, Inputs, Level 2 | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		28,242	[2],[12]	21,699	[3],[13]
Trading securities		53	[12]	44	[13]
Residential mortgage loans measured at fair value		519	[12]	561	[13]
Derivative assets		1,518	[6],[12]	1,585	[7],[13]
Total assets		30,332	[12]	23,889	[13]
Liabilities:
Derivative liabilities		836	[8],[12]	928	[9],[13]
Short positions		7	[8],[12]	5	[9],[13]
Total liabilities		843	[12]	933	[13]
Fair Value, Inputs, Level 2 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		892	[12]	888	[13]
Liabilities:
Derivative liabilities		257	[12]	276	[13]
Fair Value, Inputs, Level 2 | Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets		386	[12]	417	[13]
Liabilities:
Derivative liabilities		340	[12]	372	[13]
Fair Value, Inputs, Level 2 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets		240	[12]	280	[13]
Liabilities:
Derivative liabilities		239	[12]	280	[13]
Fair Value, Inputs, Level 2 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		1,087	[12]	1,607	[13]
Trading securities		19	[12]	14	[13]
Fair Value, Inputs, Level 2 | Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		52	[12]	192	[13]
Trading securities		9	[12]	8	[13]
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		15,081	[12]	12,404	[13]
Trading securities		6	[12]	9	[13]
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		7,862	[12]	4,565	[13]
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		2,804	[12]	1,550	[13]
Fair Value, Inputs, Level 2 | Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		1,355	[12]	1,362	[13]
Trading securities		19	[12]	13	[13]
Fair Value, Inputs, Level 2 | Equity securities | Fair value, recurring
Assets:
Available-for-sale and other securities, fair value		1	[2],[12]	19	[3],[13]
Fair Value, Inputs, Level 3 | Fair value, recurring
Assets:
Residential mortgage loans measured at fair value		167	[4]	108	[5]
Derivative assets		277	[6]	427	[7]
Total assets		444		535
Liabilities:
Derivative liabilities		64	[8]	51	[9]
Total liabilities		64		51
Fair Value, Inputs, Level 3 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		15		12
Liabilities:
Derivative liabilities		3		2
Fair Value, Inputs, Level 3 | Equity Contract | Fair value, recurring
Assets:
Derivative assets		262		415
Liabilities:
Derivative liabilities		$ 61		$ 49

[1] Amortized cost of $28,678 and $21,677 at December 31, 2015 and 2014, respectively.

[2] Excludes FHLB, FRB and DTCC restricted stock totaling $248, $355 and $1, respectively, at December 31, 2015

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

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

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

[6] Included in other assets in the Consolidated Balance Sheets.

[7] Included in other assets in the Consolidated Balance Sheets.

[8] Included in other liabilities in the Consolidated Balance Sheets

[9] Included in other liabilities in the Consolidated Balance Sheets

[10] Includes interest-only mortgage-backed securities of $50 and $175 as of December 31, 2015 and 2014, respectively, recorded at fair value with fair value changes recorded in securities gains, net, in the Consolidated Statements of Income.

[11] Equity securities consist of FHLB, FRB and DTCC restricted stock holdings of $248, $355, and $1, respectively, at December 31, 2015 and $248, $352 and $0, respectively, at December 31, 2014, that are carried at cost, and certain mutual fund and equity security holdings.

[12] During the year ended December 31, 2015, no assets or liabilities were transferred between Level 1 and Level 2

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