Composition of the Company's Loan Portfolio (Detail) - USD ($) $ in Millions		Sep. 30, 2018		Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[1]	$ 147,215		$ 143,181
Loans Held for Sale	[2]	1,961		2,290
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[3]	68,203		66,356
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		6,618		5,317
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		3,137		3,804
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		77,958		75,477
Federal National Mortgage Association (FNMA) Insured Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		452		560
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4],[5]	28,187	[6]	27,136	[7]
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	9,669		10,626
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	197		298
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		7,039		6,633
Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		10,100		8,729
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		12,010		12,140
Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,603		1,582
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		$ 69,257		$ 67,704

[1] Includes loans of consolidated VIEs of $159 million and $179 million at September 30, 2018 and December 31, 2017, respectively.

[2] Includes $1.8 billion and $1.6 billion of LHFS measured at fair value at September 30, 2018 and December 31, 2017, respectively.

[3] Includes $3.8 billion and $3.7 billion of lease financing, and $838 million and $778 million of installment loans at September 30, 2018 and December 31, 2017, respectively.

[4] Excludes $7.0 billion and $6.6 billion of guaranteed student loans and $452 million and $560 million of guaranteed residential mortgages at September 30, 2018 and December 31, 2017, respectively, for which there was nominal risk of principal loss due to the government guarantee.

[5] Includes $168 million and $196 million of LHFI measured at fair value at September 30, 2018 and December 31, 2017, respectively.

[6] Includes $168 million of loans measured at fair value, the majority of which were accruing current.

[7] Includes $196 million of loans measured at fair value, the majority of which were accruing current.