Loans and Loans Held for Sale - Loans by Category (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Residential — prime loans:
Total loans	$ 85,528	$ 60,085	$ 59,876
Commercial lease financing includes receivables held as collateral for secured borrowing	76	162	134
Purchased loans	22,400	119	114
Loans	84,663	59,295	59,080
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial, financial and agricultural	39,433	31,095	31,240
Commercial real estate:
Commercial mortgage	14,979	8,180	7,959
Construction	2,189	1,070	1,053
Total commercial real estate loans	17,168	9,250	9,012
Commercial lease financing	4,783	3,929	4,020
Total commercial/consumer loans	61,384	44,274	44,272
Residential — prime loans:
Total loans	61,384	44,274	44,272
Consumer Portfolio Segment [Member]
Commercial real estate:
Total commercial/consumer loans	24,144	15,811	15,604
Residential — prime loans:
Real estate — residential mortgage	5,509	2,267	2,242
Home equity loans	12,757	10,504	10,335
Total residential — prime loans	18,266	12,771	12,577
Consumer direct loans	1,764	1,612	1,600
Credit cards	1,084	770	806
Consumer indirect loans	3,030	658	621
Total loans	24,144	15,811	15,604
Commercial Credit Card [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial, financial and agricultural	117	88	85
PCI Loans [Member]
Residential — prime loans:
Purchased loans	959	12	11
Discontinued Operations [Member]
Residential — prime loans:
Total loans	1,625	1,891	1,824
Education Lending [Member] \| Discontinued Operations [Member]
Residential — prime loans:
Total loans	1,625	1,891	1,824
Loans	$ 1,600	$ 1,900	$ 1,800

Loans and leases receivable consumer direct loans.

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Loans and leases receivable consumer indirect loans.

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Amount before allowance of commercial leases and leveraged lease transactions where the entity is long-term creditor. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes leases covered under loss sharing agreements.

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Amount, before allowance and fees, of loans and leases receivable. Excludes loans and leases covered under loss sharing agreements.

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Reflects the aggregate value of loans, trade receivables, securities and financial instruments that serve as collateral for obligations arising from a transfer of financial assets recorded as a secured borrowing.

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Amount before allowance of revolving, open-end loan, extended under a line of credit and secured by the borrower's residential property. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount before allowance of consumer mortgage. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes subordinated loans such as home equity lines of credit and loans and leases covered under loss sharing agreements.

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Amount before allowance of consumer real estate loans. Includes, but not limited to, construction financing, residential mortgage loans, and home equity lines of credit. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount before allowance of credit card loans issued to individuals. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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Amount before allowance of commercial construction loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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Amount before allowance of loans issued to agricultural, commercial and industrial, and financial institutions. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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Amount before allowance of mortgage loans on existing land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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Amount before allowance of commercial loans issued to businesses to acquire, develop, construct, improve, or refinance land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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The cash outflow associated with purchasing loans held for investment purposes during the period.

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