Carrying Amounts and Fair Values of the Company's Financial Instruments (Detail) - USD ($)		Dec. 31, 2018		Dec. 31, 2017
Financial assets
Debt Securities, Trading, and Equity Securities, FV-NI	[1]	$ 5,506,000,000		$ 5,093,000,000
Available-for-sale Securities	[2],[3]	31,442,000,000		30,947,000,000	[4]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	[5]	1,468,000,000		2,290,000,000
Loans Held-for-sale, Fair Value Disclosure		1,200,000,000		1,600,000,000
Loans and Leases Receivable, Excluding Fair Value Loans		151,676,000,000		142,985,000,000
Loans Receivable, Fair Value Disclosure		163,000,000		196,000,000
Other Assets	[2],[6]	8,991,000,000		9,099,000,000
Financial liabilities
Deposits		162,589,000,000		160,780,000,000
Long-term Debt	[7],[8]	15,072,000,000		9,785,000,000
Long-term Debt, Fair Value		289,000,000		530,000,000
Fair Value, Inputs, Level 1 [Member]
Financial assets
Cash and Cash Equivalents, Fair Value Disclosure		7,495,000,000		6,912,000,000
Debt Securities, Trading, and Equity Securities, FV-NI		521,000,000		608,000,000
Available-for-sale Securities		4,211,000,000		4,331,000,000
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group		0		0
Loans Held-for-sale, Fair Value Disclosure		0		0
Loans and Leases Receivable, Excluding Fair Value Loans		0		0
Loans Receivable, Fair Value Disclosure		0		0
Other Assets		0		0
Other Assets, Fair Value Disclosure		95,000,000	[9]	56,000,000	[10]
Financial liabilities
Time Deposits		0		0
Short-term Debt, Fair Value		0		0
Long-term Debt		0		0
Long-term Debt, Fair Value		0		0
Trading liabilities		925,000,000		769,000,000
Fair Value, Inputs, Level 2 [Member]
Financial assets
Cash and Cash Equivalents, Fair Value Disclosure		0		0
Debt Securities, Trading, and Equity Securities, FV-NI		4,965,000,000		4,469,000,000
Available-for-sale Securities		27,231,000,000		26,544,000,000
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group		261,000,000		662,000,000
Loans Held-for-sale, Fair Value Disclosure		1,178,000,000		1,577,000,000
Loans and Leases Receivable, Excluding Fair Value Loans		0		0
Loans Receivable, Fair Value Disclosure		0		0
Other Assets		0		0
Other Assets, Fair Value Disclosure		0		0
Financial liabilities
Time Deposits		15,106,000,000		11,906,000,000
Short-term Debt, Fair Value		8,772,000,000		4,781,000,000
Long-term Debt		13,024,000,000		8,304,000,000
Long-term Debt, Fair Value		289,000,000		530,000,000
Trading liabilities		672,000,000		498,000,000
Fair Value, Inputs, Level 3 [Member]
Financial assets
Cash and Cash Equivalents, Fair Value Disclosure		0		0
Debt Securities, Trading, and Equity Securities, FV-NI		20,000,000		16,000,000
Available-for-sale Securities		0		72,000,000
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group		30,000,000		54,000,000
Loans Held-for-sale, Fair Value Disclosure		0		0
Loans and Leases Receivable, Excluding Fair Value Loans		148,167,000,000		141,379,000,000
Loans Receivable, Fair Value Disclosure		163,000,000		196,000,000
Other Assets		630,000,000	[9]	418,000,000	[10]
Other Assets, Fair Value Disclosure		0		0
Financial liabilities
Time Deposits		0		0
Short-term Debt, Fair Value		0		0
Long-term Debt		1,705,000,000		1,058,000,000
Long-term Debt, Fair Value		0		0
Trading liabilities		7,000,000		16,000,000
Reported Value Measurement [Member]
Financial assets
Cash and Cash Equivalents, Fair Value Disclosure		7,495,000,000		6,912,000,000
Debt Securities, Trading, and Equity Securities, FV-NI		5,506,000,000		5,093,000,000
Available-for-sale Securities		31,442,000,000		30,947,000,000
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group		290,000,000		713,000,000
Loans Held-for-sale, Fair Value Disclosure		1,178,000,000		1,577,000,000
Loans and Leases Receivable, Excluding Fair Value Loans		150,061,000,000		141,250,000,000
Loans Receivable, Fair Value Disclosure		163,000,000		196,000,000
Other Assets		630,000,000	[9]	418,000,000	[10]
Other Assets, Fair Value Disclosure		95,000,000	[9]	56,000,000	[10]
Financial liabilities
Time Deposits		15,355,000,000		12,076,000,000
Short-term Debt, Fair Value		8,772,000,000		4,781,000,000
Long-term Debt		14,783,000,000		9,255,000,000
Long-term Debt, Fair Value		289,000,000		530,000,000
Trading liabilities		1,604,000,000		1,283,000,000
Estimate of Fair Value, Fair Value Disclosure [Member]
Financial assets
Cash and Cash Equivalents, Fair Value Disclosure		7,495,000,000		6,912,000,000
Debt Securities, Trading, and Equity Securities, FV-NI		5,506,000,000		5,093,000,000
Available-for-sale Securities		31,442,000,000		30,947,000,000
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group		291,000,000		716,000,000
Loans Held-for-sale, Fair Value Disclosure		1,178,000,000		1,577,000,000
Loans and Leases Receivable, Excluding Fair Value Loans		148,167,000,000		141,379,000,000
Loans Receivable, Fair Value Disclosure		163,000,000		196,000,000
Other Assets		630,000,000	[9]	418,000,000	[10]
Other Assets, Fair Value Disclosure		95,000,000	[9]	56,000,000	[10]
Financial liabilities
Time Deposits		15,106,000,000		11,906,000,000
Short-term Debt, Fair Value		8,772,000,000		4,781,000,000
Long-term Debt		14,729,000,000		9,362,000,000
Long-term Debt, Fair Value		289,000,000		530,000,000
Trading liabilities		1,604,000,000		1,283,000,000
Brokered Time Deposits [Member] | Fair Value, Inputs, Level 1 [Member]
Financial liabilities
Deposits		0		0
Deposits, Fair Value Disclosure		0		0
Brokered Time Deposits [Member] | Fair Value, Inputs, Level 2 [Member]
Financial liabilities
Deposits		615,000,000		725,000,000
Deposits, Fair Value Disclosure		403,000,000		236,000,000
Brokered Time Deposits [Member] | Fair Value, Inputs, Level 3 [Member]
Financial liabilities
Deposits		0		0
Deposits, Fair Value Disclosure		0		0
Brokered Time Deposits [Member] | Reported Value Measurement [Member]
Financial liabilities
Deposits		642,000,000		749,000,000
Deposits, Fair Value Disclosure		403,000,000		236,000,000
Brokered Time Deposits [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Financial liabilities
Deposits		615,000,000		725,000,000
Deposits, Fair Value Disclosure		$ 403,000,000		$ 236,000,000

[1] Includes trading securities pledged as collateral where counterparties have the right to sell or repledge the collateral of $1,442 million and $1,086 million at December?31, 2018 and December?31, 2017, respectively.

[2] Beginning January 1, 2018, the Company reclassified equity securities previously presented in Securities available for sale to Other assets. Reclassifications have been made to previously reported amounts for comparability.

[3] Includes securities AFS pledged as collateral where counterparties have the right to sell or repledge the collateral of $222 million and $223 million at December?31, 2018 and December?31, 2017, respectively.

[4] Beginning January 1, 2018, the Company reclassified equity securities previously presented in Securities AFS to Other assets on the Consolidated Balance Sheets. Prior periods have been revised to conform to the current presentation for comparability. See Note 11, "Other Assets," for additional information.

[5] Includes $1.2 billion and $1.6 billion of LHFS measured at fair value at December 31, 2018 and 2017, respectively.

[6] Beginning October 1, 2018, the Company reclassified software and related accumulated amortization previously presented in Other assets to Premises, property, and equipment, net. Reclassifications have been made to previously reported amounts for comparability.

[7] Includes $289 million and $530 million of long-term debt measured at fair value at December 31, 2018 and 2017, respectively.

[8] Includes debt of consolidated VIEs of $161 million and $189 million at December?31, 2018 and December?31, 2017, respectively.

[9] Other financial assets recorded at amortized cost consist of FHLB of Atlanta stock and Federal Reserve Bank of Atlanta stock. Other financial assets recorded at fair value consist of mutual fund investments and other equity securities with readily determinable fair values.

[10] Other financial assets recorded at amortized cost consist of FHLB of Atlanta stock and Federal Reserve Bank of Atlanta stock. Other financial assets recorded at fair value consist of mutual fund investments and other equity securities with readily determinable fair values.