Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Millions		Jun. 30, 2016		Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets	[1]	$ 6,850		$ 6,119
Available-for-sale Securities		29,336		27,825
Loans Held-for-sale, Fair Value Disclosure		2,176		1,494
Loans Receivable, Fair Value Disclosure		246		257
Servicing Asset at Fair Value, Amount		1,061
Long-term Debt, Fair Value		970
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets	[2]	909		866
Available-for-sale Securities	[2]	4,525		3,542
Loans Held-for-sale, Fair Value Disclosure	[3]	0		0
Trading Liabilities, Fair Value Disclosure	[2]	637		664
Long-term Debt, Fair Value	[4]	0		0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets	[2]	5,868		5,143
Available-for-sale Securities	[2]	24,098		23,727
Loans Held-for-sale, Fair Value Disclosure	[3]	2,400		1,803
Trading Liabilities, Fair Value Disclosure	[2]	595		593
Long-term Debt, Fair Value	[4]	11,557		7,772
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets	[2]	73		110
Available-for-sale Securities	[2]	713		556
Loans Held-for-sale, Fair Value Disclosure	[3]	75		39
Trading Liabilities, Fair Value Disclosure	[2]	13		6
Long-term Debt, Fair Value	[4]	682		602
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		6,850		6,119
Trading Liabilities, Fair Value Disclosure		1,245		1,263
Deposits, Fair Value Disclosure		49
Other Liabilities, Fair Value Disclosure	[5]			23
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		909		866
Available-for-sale Securities		4,525		3,542
Loans Held-for-sale, Fair Value Disclosure		0		0
Loans Receivable, Fair Value Disclosure		0		0
Servicing Asset at Fair Value, Amount		0		0
Trading Liabilities, Fair Value Disclosure		637		664
Deposits, Fair Value Disclosure		0
Long-term Debt, Fair Value		0		0
Other Liabilities, Fair Value Disclosure	[5]			0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		10,797		8,456
Available-for-sale Securities		24,098		23,727
Loans Held-for-sale, Fair Value Disclosure		2,172		1,489
Loans Receivable, Fair Value Disclosure		0		0
Servicing Asset at Fair Value, Amount		0		0
Trading Liabilities, Fair Value Disclosure		6,028		4,557
Deposits, Fair Value Disclosure		49
Long-term Debt, Fair Value		970		973
Other Liabilities, Fair Value Disclosure	[5]			0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		73		110
Available-for-sale Securities		713		556
Loans Held-for-sale, Fair Value Disclosure		4		5
Loans Receivable, Fair Value Disclosure		246		257
Servicing Asset at Fair Value, Amount		1,061		1,307
Trading Liabilities, Fair Value Disclosure		13		6
Deposits, Fair Value Disclosure		0
Long-term Debt, Fair Value		0		0
Other Liabilities, Fair Value Disclosure	[5]			23
US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		531		538
Available-for-sale Securities		4,441		3,449
Trading Liabilities, Fair Value Disclosure		473		503
US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Available-for-sale Securities		0		0
Trading Liabilities, Fair Value Disclosure		0		0
US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Available-for-sale Securities		0		0
Trading Liabilities, Fair Value Disclosure		0		0
US Government Agencies Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Available-for-sale Securities		0		0
US Government Agencies Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		396		588
Available-for-sale Securities		372		411
US Government Agencies Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Available-for-sale Securities		0		0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Available-for-sale Securities		0		0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		54		30
Available-for-sale Securities		171		159
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Available-for-sale Securities		4		5
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Available-for-sale Securities		0		0
Trading Liabilities, Fair Value Disclosure		0		0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		826		553
Available-for-sale Securities		23,524		23,124
Trading Liabilities, Fair Value Disclosure		3		37
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Available-for-sale Securities		0		0
Trading Liabilities, Fair Value Disclosure		0		0
Collateralized Loan Obligations [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Collateralized Loan Obligations [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		3		2
Collateralized Loan Obligations [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Other Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Available-for-sale Securities		0		0
Trading Liabilities, Fair Value Disclosure		0		0
Other Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		499		379
Available-for-sale Securities		31		33
Trading Liabilities, Fair Value Disclosure		311		259
Other Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		89
Available-for-sale Securities		5		5
Trading Liabilities, Fair Value Disclosure		0		0
Commercial Paper [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Commercial Paper [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		139		67
Commercial Paper [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		53		66
Available-for-sale Securities		84	[6]	93	[7]
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Available-for-sale Securities		0	[6]	0	[7]
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Available-for-sale Securities		610	[6]	440	[7]
Derivative Financial Instruments, Assets [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		1,669		1,152
Derivative Financial Instruments, Assets [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		325		262
Derivative Financial Instruments, Assets [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		6,200		4,182
Derivative Financial Instruments, Assets [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		73		21
Trading Loans [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Trading Loans [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		2,680		2,655
Trading Loans [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		0		0
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0		0
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0		0
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		83		94
Asset-backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0		0
Asset-backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		0		0
Asset-backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		11		12
Derivative Financial Instruments, Liabilities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Liabilities, Fair Value Disclosure		458		464
Derivative Financial Instruments, Liabilities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Liabilities, Fair Value Disclosure		164		161
Derivative Financial Instruments, Liabilities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Liabilities, Fair Value Disclosure		5,714		4,261
Derivative Financial Instruments, Liabilities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Liabilities, Fair Value Disclosure		13		6
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets	[2]	6,850		6,119
Available-for-sale Securities	[2]	29,336		27,825
Loans Held-for-sale, Fair Value Disclosure	[3]	2,475		1,842
Trading Liabilities, Fair Value Disclosure	[2]	1,245		1,263
Long-term Debt, Fair Value	[4]	12,239		8,374
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		29,336		27,825
Loans Held-for-sale, Fair Value Disclosure		2,176		1,494
Loans Receivable, Fair Value Disclosure		246		257
Servicing Asset at Fair Value, Amount		1,061		1,307
Long-term Debt, Fair Value		970		973
Estimate of Fair Value Measurement [Member] | US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		531		538
Available-for-sale Securities		4,441		3,449
Trading Liabilities, Fair Value Disclosure		473		503
Estimate of Fair Value Measurement [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		396		588
Available-for-sale Securities		372		411
Estimate of Fair Value Measurement [Member] | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		54		30
Available-for-sale Securities		175		164
Estimate of Fair Value Measurement [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		826		553
Available-for-sale Securities		23,524		23,124
Trading Liabilities, Fair Value Disclosure		3		37
Estimate of Fair Value Measurement [Member] | Collateralized Loan Obligations [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		3		2
Estimate of Fair Value Measurement [Member] | Other Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		499		468
Available-for-sale Securities		36		38
Trading Liabilities, Fair Value Disclosure		311		259
Estimate of Fair Value Measurement [Member] | Commercial Paper [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		139		67
Estimate of Fair Value Measurement [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		53		66
Available-for-sale Securities		694	[6]	533	[7]
Estimate of Fair Value Measurement [Member] | Trading Loans [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		2,680		2,655
Estimate of Fair Value Measurement [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		83		94
Estimate of Fair Value Measurement [Member] | Asset-backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities		11		12
Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets	[2]	6,850		6,119
Available-for-sale Securities	[2]	29,336		27,825
Loans Held-for-sale, Fair Value Disclosure	[3]	2,468		1,838
Trading Liabilities, Fair Value Disclosure	[2]	1,245		1,263
Long-term Debt, Fair Value	[4]	12,264		8,462
Netting [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		(4,929)	[8]	(3,313)	[9]
Trading Liabilities, Fair Value Disclosure		(5,433)	[8]	(3,964)	[9]
Netting [Member] | Derivative Financial Instruments, Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading assets		(4,929)	[8]	(3,313)	[9]
Netting [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Liabilities, Fair Value Disclosure		$ (5,433)	[8]	$ (3,964)	[9]

[1] Includes trading securities pledged as collateral where counterparties have the right to sell or repledge the collateral of $1,282 million and $1,377 million at June 30, 2016 and December 31, 2015, respectively

[2] Trading assets and derivative instruments, securities AFS, and trading liabilities and derivative instruments that are classified as level 1 are valued based on quoted market prices. For those instruments classified as level 2 or 3, refer to the respective valuation discussions within this footnote.

[3] LHFS are generally valued based on observable current market prices or, if quoted market prices are not available, quoted market prices of similar instruments. Refer to the LHFS section within this footnote for further discussion. When valuation assumptions are not readily observable in the market, instruments are valued based on the best available data to approximate fair value. This data may be internally developed and considers risk premiums that a market participant would require under then-current market conditions.

[4] Fair values for short-term borrowings and certain long-term debt are based on quoted market prices for similar instruments or estimated discounted cash flows utilizing the Company’s current incremental borrowing rate for similar types of instruments. For long-term debt that the Company measures at fair value, refer to the respective valuation section within this footnote. For level 3 debt, the terms are unique in nature or there are no similar instruments that can be used to value the instrument without using significant unobservable assumptions. In these situations, the Company reviews current borrowing rates along with the collateral levels that secure the debt in determining an appropriate fair value adjustment.

[5] Includes contingent consideration obligations related to acquisitions.

[6] Includes $84 million of mutual fund investments, $202 million of FHLB of Atlanta stock, $402 million of Federal Reserve Bank of Atlanta stock, and $6 million of other.

[7] Includes $93 million of mutual fund investments, $32 million of FHLB of Atlanta stock, $402 million of Federal Reserve Bank of Atlanta stock, and $6 million of other.

[8] Amounts represent offsetting cash collateral received from, and paid to, the same derivative counterparties, and the impact of netting derivative assets and derivative liabilities when a legally enforceable master netting agreement or similar agreement exists.

[9] Amounts represent offsetting cash collateral received from, and paid to, the same derivative counterparties, and the impact of netting derivative assets and derivative liabilities when a legally enforceable master netting agreement or similar agreement exists.