Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Millions		Mar. 31, 2016		Dec. 31, 2015
Assets:
Available-for-sale securities, fair value	[1]	$ 29,891		$ 29,044
Trading securities		405		386
Fair value, recurring
Assets:
Available-for-sale securities, fair value		29,287	[2]	28,440	[3]
Trading securities		405		386
Residential mortgage loans held for sale		600		519
Residential mortgage loans measured at FV		160	[4]	167	[5]
Derivative assets	[6]	2,126		1,852
Total assets		32,578		31,364
Liabilities:
Derivative liabilities	[7]	967		938
Short positions	[7]	24		29
Total liabilities		991		967
Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		1,300		910
Liabilities:
Derivative liabilities		429		261
Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets		285		386
Liabilities:
Derivative liabilities		272		340
Equity Contract | Fair value, recurring
Assets:
Derivative assets		308		262
Liabilities:
Derivative liabilities		55		61
Commodity Contract | Fair value, recurring
Assets:
Derivative assets		233		294
Liabilities:
Derivative liabilities		211		276
U.S. Treasury and federal agencies
Assets:
Available-for-sale securities, fair value		1,161		1,187
U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale securities, fair value		1,161		1,187
Trading securities		18		19
Obligations of states and political subdivisions
Assets:
Available-for-sale securities, fair value		52		52
Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale securities, fair value		52		52
Trading securities		54		9
Agency mortgage-backed securities | Residential mortgage backed securities
Assets:
Available-for-sale securities, fair value		15,129	[8]	15,081	[9]
Agency mortgage-backed securities | Residential mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		15,129		15,081
Trading securities		5		6
Agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member]
Assets:
Available-for-sale securities, fair value		8,205		7,862
Agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale securities, fair value		8,205		7,862
Trading securities		1
Non-agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member]
Assets:
Available-for-sale securities, fair value		3,120		2,804
Non-agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale securities, fair value		3,120		2,804
Asset-backed securities and other debt securities
Assets:
Available-for-sale securities, fair value		1,520		1,355
Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		1,520		1,355
Trading securities		23		19
Equity securities
Assets:
Available-for-sale securities, fair value		704	[10]	703	[11]
Equity securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		100	[2]	99	[3]
Trading securities		304		333
Fair Value, Inputs, Level 1 | Fair value, recurring
Assets:
Available-for-sale securities, fair value		176	[2],[12]	198	[3],[13]
Trading securities		305	[12]	333	[13]
Derivative assets	[6]	38	[12]	57	[13]
Total assets		519	[12]	588	[13]
Liabilities:
Derivative liabilities	[7]	30	[12]	38	[13]
Short positions	[7]	15	[12]	22	[13]
Total liabilities		45	[12]	60	[13]
Fair Value, Inputs, Level 1 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		1	[12]	3	[13]
Liabilities:
Derivative liabilities		9	[12]	1	[13]
Fair Value, Inputs, Level 1 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets		37	[12]	54	[13]
Liabilities:
Derivative liabilities		21	[12]	37	[13]
Fair Value, Inputs, Level 1 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale securities, fair value		77	[12]	100	[13]
Trading securities	[12]	1
Fair Value, Inputs, Level 1 | Equity securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		99	[2],[12]	98	[3],[13]
Trading securities		304	[12]	333	[13]
Fair Value, Inputs, Level 2 | Fair value, recurring
Assets:
Available-for-sale securities, fair value		29,111	[2],[12]	28,242	[3],[13]
Trading securities		100	[12]	53	[13]
Residential mortgage loans held for sale		600	[12]	519	[13]
Derivative assets	[6]	1,751	[12]	1,518	[13]
Total assets		31,562	[12]	30,332	[13]
Liabilities:
Derivative liabilities	[7]	878	[12]	836	[13]
Short positions	[7]	9	[12]	7	[13]
Total liabilities		887	[12]	843	[13]
Fair Value, Inputs, Level 2 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		1,270	[12]	892	[13]
Liabilities:
Derivative liabilities		416	[12]	257	[13]
Fair Value, Inputs, Level 2 | Foreign Exchange Contract | Fair value, recurring
Assets:
Derivative assets		285	[12]	386	[13]
Liabilities:
Derivative liabilities		272	[12]	340	[13]
Fair Value, Inputs, Level 2 | Commodity Contract | Fair value, recurring
Assets:
Derivative assets		196	[12]	240	[13]
Liabilities:
Derivative liabilities		190	[12]	239	[13]
Fair Value, Inputs, Level 2 | U.S. Treasury and federal agencies | Fair value, recurring
Assets:
Available-for-sale securities, fair value		1,084	[12]	1,087	[13]
Trading securities		17	[12]	19	[13]
Fair Value, Inputs, Level 2 | Obligations of states and political subdivisions | Fair value, recurring
Assets:
Available-for-sale securities, fair value		52	[12]	52	[13]
Trading securities		54	[12]	9	[13]
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Residential mortgage backed securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		15,129	[12]	15,081	[13]
Trading securities		5	[12]	6	[13]
Fair Value, Inputs, Level 2 | Agency mortgage-backed securities | Commercial Mortgage Backed Securities [Member] | Fair value, recurring
Assets:
Available-for-sale securities, fair value		8,205	[12]	7,862	[13]
Trading securities	[12]	1
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		3,120	[12]	2,804	[13]
Fair Value, Inputs, Level 2 | Asset-backed securities and other debt securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		1,520	[12]	1,355	[13]
Trading securities		23	[12]	19	[13]
Fair Value, Inputs, Level 2 | Equity securities | Fair value, recurring
Assets:
Available-for-sale securities, fair value		1	[2],[12]	1	[3],[13]
Fair Value, Inputs, Level 3 | Fair value, recurring
Assets:
Residential mortgage loans measured at FV		160	[4]	167	[5]
Derivative assets	[6]	337		277
Total assets		497		444
Liabilities:
Derivative liabilities	[7]	59		64
Total liabilities		59		64
Fair Value, Inputs, Level 3 | Interest Rate Contract | Fair value, recurring
Assets:
Derivative assets		29		15
Liabilities:
Derivative liabilities		4		3
Fair Value, Inputs, Level 3 | Equity Contract | Fair value, recurring
Assets:
Derivative assets		308		262
Liabilities:
Derivative liabilities		$ 55		$ 61

[1] Amortized cost of $28,838 and $28,678 at March 31, 2016 and December 31, 2015, respectively.

[2] Excludes FHLB, FRB and DTCC restricted stock holdings totaling $248, $355 and $1 respectively, at March 31, 2016.

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

[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 Condensed Consolidated Balance Sheets.

[7] Included in other liabilities in the Condensed Consolidated Balance Sheets.

[8] Includes interest-only mortgage-backed securities of $41 as of March 31, 2016 recorded at fair value with fair value changes recorded in securities gains, net, in the Condensed Consolidated Statements of Income.

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

[10] Equity securities consist of FHLB, FRB and DTCC restricted stock holdings of $248, $355 and $1, respectively, at March 31, 2016, that are carried at cost, and certain mutual fund and equity security holdings.

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

[12] During the three months ended March 31, 2016, no assets or liabilities were transferred between Level 1 and Level 2.

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