Fair Value Measurements - Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	$ 867,000,000	$ 788,000,000
Securities available for sale	20,212,000,000	14,218,000,000
Loans net of deferred income	86,038,000,000	59,876,000,000	$ 57,381,000,000
Loans held for sale	0	0
Netting adjustments	(431,000,000)	(866,000,000)
Total derivative assets	803,000,000	619,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Netting adjustments	(384,000,000)	(494,000,000)
Total derivative liabilities	636,000,000	632,000,000
Collateralized Mortgage Obligations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	16,408,000,000	11,995,000,000
U.S. Treasury, Agencies and Corporations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	184,000,000	0
States and Political Subdivisions [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	11,000,000	14,000,000
Other Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	20,000,000	20,000,000
Residential Mortgage Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	1,846,000,000	2,189,000,000
Other Mortgage-Backed Securities [Member] | Commercial Mortgage Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	1,743,000,000	0
Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Commercial loans	18,000,000	6,000,000
Total trading account assets	867,000,000	788,000,000
Securities available for sale	20,212,000,000	14,218,000,000
Total other investments	191,000,000	312,000,000
Loans net of deferred income	0
Loans held for sale	62,000,000
Derivative assets	1,234,000,000	1,485,000,000
Netting adjustments	(431,000,000)	(866,000,000)
Total derivative assets	803,000,000	619,000,000
Accrued income and other assets	8,000,000	1,000,000
Total assets on a recurring basis at fair value	22,143,000,000	15,938,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1,020,000,000	1,126,000,000
Netting adjustments	(384,000,000)	(494,000,000)
Total derivative liabilities	636,000,000	632,000,000
Accrued expense and other liabilities	14,000,000	1,000,000
Total liabilities on a recurring basis at fair value	1,458,000,000	1,166,000,000
Recurring [Member] | Collateralized Mortgage Obligations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	16,408,000,000	11,995,000,000
Recurring [Member] | Trading Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	849,000,000	782,000,000
Recurring [Member] | U.S. Treasury, Agencies and Corporations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	655,000,000	704,000,000
Securities available for sale	184,000,000
Recurring [Member] | States and Political Subdivisions [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	8,000,000	25,000,000
Securities available for sale	11,000,000	14,000,000
Recurring [Member] | Other Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	73,000,000	27,000,000
Securities available for sale	20,000,000	20,000,000
Recurring [Member] | Commercial Mortgage Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	1,743,000,000
Recurring [Member] | Principal Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	27,000,000	69,000,000
Recurring [Member] | Principal Indirect Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	158,000,000	235,000,000
Recurring [Member] | Principal Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	185,000,000	304,000,000
Recurring [Member] | Equity and Mezzanine Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	6,000,000	8,000,000
Recurring [Member] | Private Equity and Mezzanine Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	6,000,000	8,000,000
Recurring [Member] | Other Mortgage-Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	113,000,000	26,000,000
Recurring [Member] | Other Mortgage-Backed Securities [Member] | Residential Mortgage Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	1,846,000,000	2,189,000,000
Recurring [Member] | Short Positions [Member]
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	808,000,000	533,000,000
Recurring [Member] | Interest Rate [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	930,000,000	884,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	737,000,000	563,000,000
Recurring [Member] | Foreign Exchange [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	123,000,000	151,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	113,000,000	124,000,000
Recurring [Member] | Commodity [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	176,000,000	444,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	165,000,000	433,000,000
Recurring [Member] | Credit [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	1,000,000	6,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	4,000,000	6,000,000
Recurring [Member] | Other Credit Derivatives [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	4,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1,000,000
Level 1 [Member] | Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Commercial loans	0	0
Total trading account assets	0	3,000,000
Securities available for sale	3,000,000	3,000,000
Total other investments	0	0
Loans net of deferred income	0
Loans held for sale	0
Derivative assets	114,000,000	143,000,000
Netting adjustments	0	0
Total derivative assets	114,000,000	143,000,000
Accrued income and other assets	0	0
Total assets on a recurring basis at fair value	117,000,000	149,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	102,000,000	116,000,000
Netting adjustments	0	0
Total derivative liabilities	102,000,000	116,000,000
Accrued expense and other liabilities	0	0
Total liabilities on a recurring basis at fair value	294,000,000	116,000,000
Level 1 [Member] | Recurring [Member] | Collateralized Mortgage Obligations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	0	0
Level 1 [Member] | Recurring [Member] | Trading Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	3,000,000
Level 1 [Member] | Recurring [Member] | U.S. Treasury, Agencies and Corporations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	0
Level 1 [Member] | Recurring [Member] | States and Political Subdivisions [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	0	0
Level 1 [Member] | Recurring [Member] | Other Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	3,000,000
Securities available for sale	3,000,000	3,000,000
Level 1 [Member] | Recurring [Member] | Commercial Mortgage Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	0
Level 1 [Member] | Recurring [Member] | Principal Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 1 [Member] | Recurring [Member] | Principal Indirect Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 1 [Member] | Recurring [Member] | Principal Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 1 [Member] | Recurring [Member] | Equity and Mezzanine Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 1 [Member] | Recurring [Member] | Private Equity and Mezzanine Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 1 [Member] | Recurring [Member] | Other Mortgage-Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Level 1 [Member] | Recurring [Member] | Other Mortgage-Backed Securities [Member] | Residential Mortgage Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	0	0
Level 1 [Member] | Recurring [Member] | Short Positions [Member]
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	192,000,000	0
Level 1 [Member] | Recurring [Member] | Interest Rate [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Level 1 [Member] | Recurring [Member] | Foreign Exchange [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	114,000,000	143,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	102,000,000	116,000,000
Level 1 [Member] | Recurring [Member] | Commodity [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Level 1 [Member] | Recurring [Member] | Credit [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Level 1 [Member] | Recurring [Member] | Other Credit Derivatives [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0
Level 2 [Member] | Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Commercial loans	18,000,000	6,000,000
Total trading account assets	867,000,000	785,000,000
Securities available for sale	20,192,000,000	14,198,000,000
Total other investments	0	19,000,000
Loans net of deferred income	0
Loans held for sale	62,000,000
Derivative assets	1,110,000,000	1,324,000,000
Netting adjustments	0	0
Total derivative assets	1,110,000,000	1,324,000,000
Accrued income and other assets	8,000,000	1,000,000
Total assets on a recurring basis at fair value	22,239,000,000	16,327,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	918,000,000	1,009,000,000
Netting adjustments	0	0
Total derivative liabilities	918,000,000	1,009,000,000
Accrued expense and other liabilities	14,000,000	1,000,000
Total liabilities on a recurring basis at fair value	1,548,000,000	1,543,000,000
Level 2 [Member] | Recurring [Member] | Collateralized Mortgage Obligations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	16,408,000,000	11,995,000,000
Level 2 [Member] | Recurring [Member] | Trading Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	849,000,000	779,000,000
Level 2 [Member] | Recurring [Member] | U.S. Treasury, Agencies and Corporations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	655,000,000	704,000,000
Securities available for sale	184,000,000
Level 2 [Member] | Recurring [Member] | States and Political Subdivisions [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	8,000,000	25,000,000
Securities available for sale	11,000,000	14,000,000
Level 2 [Member] | Recurring [Member] | Other Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	73,000,000	24,000,000
Securities available for sale	0	0
Level 2 [Member] | Recurring [Member] | Commercial Mortgage Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	1,743,000,000
Level 2 [Member] | Recurring [Member] | Principal Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	19,000,000
Level 2 [Member] | Recurring [Member] | Principal Indirect Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 2 [Member] | Recurring [Member] | Principal Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	19,000,000
Level 2 [Member] | Recurring [Member] | Equity and Mezzanine Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 2 [Member] | Recurring [Member] | Private Equity and Mezzanine Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 2 [Member] | Recurring [Member] | Other Mortgage-Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	113,000,000	26,000,000
Level 2 [Member] | Recurring [Member] | Other Mortgage-Backed Securities [Member] | Residential Mortgage Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	1,846,000,000	2,189,000,000
Level 2 [Member] | Recurring [Member] | Short Positions [Member]
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	616,000,000	533,000,000
Level 2 [Member] | Recurring [Member] | Interest Rate [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	923,000,000	868,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	737,000,000	563,000,000
Level 2 [Member] | Recurring [Member] | Foreign Exchange [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	9,000,000	8,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	11,000,000	8,000,000
Level 2 [Member] | Recurring [Member] | Commodity [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	176,000,000	444,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	165,000,000	433,000,000
Level 2 [Member] | Recurring [Member] | Credit [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	4,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	4,000,000	5,000,000
Level 2 [Member] | Recurring [Member] | Other Credit Derivatives [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	2,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1,000,000
Level 3 [Member] | Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Commercial loans	0	0
Total trading account assets	0	0
Securities available for sale	17,000,000	17,000,000
Total other investments	27,000,000	50,000,000
Loans net of deferred income	0
Loans held for sale	0
Derivative assets	10,000,000	18,000,000
Netting adjustments	0	0
Total derivative assets	10,000,000	18,000,000
Accrued income and other assets	0	0
Total assets on a recurring basis at fair value	54,000,000	85,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	1,000,000
Netting adjustments	0	0
Total derivative liabilities	0	1,000,000
Accrued expense and other liabilities	0	0
Total liabilities on a recurring basis at fair value	0	1,000,000
Level 3 [Member] | Recurring [Member] | Collateralized Mortgage Obligations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	0	0
Level 3 [Member] | Recurring [Member] | Trading Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Level 3 [Member] | Recurring [Member] | U.S. Treasury, Agencies and Corporations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	0
Level 3 [Member] | Recurring [Member] | States and Political Subdivisions [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	0	0
Level 3 [Member] | Recurring [Member] | Other Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Securities available for sale	17,000,000	17,000,000
Level 3 [Member] | Recurring [Member] | Commercial Mortgage Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	0
Level 3 [Member] | Recurring [Member] | Principal Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	27,000,000	50,000,000
Level 3 [Member] | Recurring [Member] | Principal Indirect Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 3 [Member] | Recurring [Member] | Principal Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	27,000,000	50,000,000
Level 3 [Member] | Recurring [Member] | Equity and Mezzanine Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 3 [Member] | Recurring [Member] | Private Equity and Mezzanine Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	0	0
Level 3 [Member] | Recurring [Member] | Other Mortgage-Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	0	0
Level 3 [Member] | Recurring [Member] | Other Mortgage-Backed Securities [Member] | Residential Mortgage Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities available for sale	0	0
Level 3 [Member] | Recurring [Member] | Short Positions [Member]
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Level 3 [Member] | Recurring [Member] | Interest Rate [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	7,000,000	16,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Level 3 [Member] | Recurring [Member] | Foreign Exchange [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Level 3 [Member] | Recurring [Member] | Commodity [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	0	0
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	0
Level 3 [Member] | Recurring [Member] | Credit [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	1,000,000	2,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	0	$ 1,000,000
Level 3 [Member] | Recurring [Member] | Other Credit Derivatives [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	2,000,000
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	$ 0