Composition of the Company's Loan Portfolio (Detail) - USD ($) $ in Millions		Dec. 31, 2017		Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[1]	$ 143,181		$ 143,298
Loans Held for Sale	[2]	2,290		4,169
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[3]	66,356		69,213
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		5,317		4,996
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		3,804		4,015
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		75,477		78,224
Federal National Mortgage Association (FNMA) Insured Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		560		537
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4],[5]	27,136	[6]	26,137	[7]
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	10,626		11,912
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	298		404
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		6,633		6,167
Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		8,729		7,771
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		12,140		10,736
Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,582		1,410
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		$ 67,704		$ 65,074

[1] Includes loans of consolidated VIEs of $179 million and $211 million at December 31, 2017 and December 31, 2016, respectively.

[2] Includes $1.6 billion and $3.5 billion of LHFS measured at fair value at December 31, 2017 and 2016, respectively.

[3] Includes $3.7 billion of lease financing at both December 31, 2017 and 2016, and $778 million and $729 million of installment loans at December 31, 2017 and 2016, respectively.

[4] Excludes $6.6 billion and $6.2 billion of guaranteed student loans and $560 million and $537 million of guaranteed residential mortgages at December 31, 2017 and 2016, respectively, for which there was nominal risk of principal loss due to the government guarantee.

[5] Includes $196 million and $222 million of LHFI measured at fair value at December 31, 2017 and 2016, respectively.

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

[7] Includes $222 million of loans measured at fair value, the majority of which were accruing current.