Carrying Amounts and Fair Values of the Company's Financial Instruments (Detail) - USD ($)		Jun. 30, 2019		Dec. 31, 2018
Financial assets
Debt Securities, Trading, and Equity Securities, FV-NI	[1]	$ 6,610,000,000		$ 5,506,000,000
Available-for-sale Securities	[2]	32,487,000,000		31,442,000,000
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	[3]	2,229,000,000		1,468,000,000
Loans and Leases Receivable, Excluding Fair Value Loans		156,462,000,000		151,676,000,000
Loans Receivable, Fair Value Disclosure		127,000,000		163,000,000
Other Assets		10,936,000,000		8,991,000,000
Financial liabilities
Deposits		161,132,000,000		162,589,000,000
Long-term Debt	[4]	20,200,000,000		15,072,000,000
Fair Value, Inputs, Level 1 [Member]
Financial assets
Cash and Cash Equivalents, Fair Value Disclosure		5,028,000,000		7,495,000,000
Debt Securities, Trading, and Equity Securities, FV-NI		663,000,000		521,000,000
Available-for-sale Securities		4,345,000,000		4,211,000,000
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		87,000,000	[5]	95,000,000	[6]
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		716,000,000		925,000,000
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		5,915,000,000		4,965,000,000
Available-for-sale Securities		28,142,000,000		27,231,000,000
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group		512,000,000		261,000,000
Loans Held-for-sale, Fair Value Disclosure		1,695,000,000		1,178,000,000
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		16,613,000,000		15,106,000,000
Short-term Debt, Fair Value		9,524,000,000		8,772,000,000
Long-term Debt		18,464,000,000		13,024,000,000
Long-term Debt, Fair Value		302,000,000		289,000,000
Trading liabilities		570,000,000		672,000,000
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		32,000,000		20,000,000
Available-for-sale Securities		0		0
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group		24,000,000		30,000,000
Loans Held-for-sale, Fair Value Disclosure		0		0
Loans and Leases Receivable, Excluding Fair Value Loans		154,748,000,000		148,167,000,000
Loans Receivable, Fair Value Disclosure		127,000,000		163,000,000
Other Assets		832,000,000	[5]	630,000,000	[6]
Other Assets, Fair Value Disclosure		0		0
Financial liabilities
Time Deposits		0		0
Short-term Debt, Fair Value		0		0
Long-term Debt		1,589,000,000		1,705,000,000
Long-term Debt, Fair Value		0		0
Trading liabilities		8,000,000		7,000,000
Reported Value Measurement [Member]
Financial assets
Cash and Cash Equivalents, Fair Value Disclosure		5,028,000,000		7,495,000,000
Debt Securities, Trading, and Equity Securities, FV-NI		6,610,000,000		5,506,000,000
Available-for-sale Securities		32,487,000,000		31,442,000,000
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group		534,000,000		290,000,000
Loans Held-for-sale, Fair Value Disclosure		1,695,000,000		1,178,000,000
Loans and Leases Receivable, Excluding Fair Value Loans		154,781,000,000		150,061,000,000
Loans Receivable, Fair Value Disclosure		127,000,000		163,000,000
Other Assets		832,000,000	[5]	630,000,000	[6]
Other Assets, Fair Value Disclosure		87,000,000	[5]	95,000,000	[6]
Financial liabilities
Time Deposits		16,732,000,000		15,355,000,000
Short-term Debt, Fair Value		9,524,000,000		8,772,000,000
Long-term Debt		19,898,000,000		14,783,000,000
Long-term Debt, Fair Value		302,000,000		289,000,000
Trading liabilities		1,294,000,000		1,604,000,000
Estimate of Fair Value, Fair Value Disclosure [Member]
Financial assets
Cash and Cash Equivalents, Fair Value Disclosure		5,028,000,000		7,495,000,000
Debt Securities, Trading, and Equity Securities, FV-NI		6,610,000,000		5,506,000,000
Available-for-sale Securities		32,487,000,000		31,442,000,000
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group		536,000,000		291,000,000
Loans Held-for-sale, Fair Value Disclosure		1,695,000,000		1,178,000,000
Loans and Leases Receivable, Excluding Fair Value Loans		154,748,000,000		148,167,000,000
Loans Receivable, Fair Value Disclosure		127,000,000		163,000,000
Other Assets		832,000,000	[5]	630,000,000	[6]
Other Assets, Fair Value Disclosure		87,000,000	[5]	95,000,000	[6]
Financial liabilities
Time Deposits		16,613,000,000		15,106,000,000
Short-term Debt, Fair Value		9,524,000,000		8,772,000,000
Long-term Debt		20,053,000,000		14,729,000,000
Long-term Debt, Fair Value		302,000,000		289,000,000
Trading liabilities		1,294,000,000		1,604,000,000
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		864,000,000		615,000,000
Deposits, Fair Value Disclosure		524,000,000		403,000,000
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		890,000,000		642,000,000
Deposits, Fair Value Disclosure		524,000,000		403,000,000
Brokered Time Deposits [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Financial liabilities
Deposits		864,000,000		615,000,000
Deposits, Fair Value Disclosure		$ 524,000,000		$ 403,000,000

[1] Includes trading securities pledged as collateral where counterparties have the right to sell or repledge the collateral of $1,214 million and $1,442 million at June 30, 2019 and December 31, 2018, respectively.

[2] Includes securities AFS pledged as collateral where counterparties have the right to sell or repledge the collateral of $212 million and $222 million at June 30, 2019 and December 31, 2018, respectively.

[3] Includes $1.7 billion and $1.2 billion of LHFS measured at fair value at June 30, 2019 and December 31, 2018, respectively.

[4] Includes debt of consolidated VIEs of $149 million and $161 million at June 30, 2019 and December 31, 2018, respectively.

[5] 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.

[6] 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.