Guarantees and Contingent Liabilities - Summary of Other Guarantees and Contingent Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Standby Letters of Credit [Member]
Guarantor Obligations [Line Items]
Carrying Amount	$ 63
Maximum Potential Future Payments	12,326
Third Party Borrowing Arrangements [Member]
Guarantor Obligations [Line Items]
Maximum Potential Future Payments	13
Securities Lending Indemnifications [Member]
Guarantor Obligations [Line Items]
Collateral Held	3,442
Maximum Potential Future Payments	3,382
Asset Sales [Member]
Guarantor Obligations [Line Items]
Carrying Amount	105
Maximum Potential Future Payments	5,799
Merchant Processing [Member]
Guarantor Obligations [Line Items]
Collateral Held	552
Carrying Amount	57
Maximum Potential Future Payments	96,919
Tender Option Bond Program Guarantee [Member]
Guarantor Obligations [Line Items]
Collateral Held	1,051
Maximum Potential Future Payments	1,028
Minimum Revenue Guarantees [Member]
Guarantor Obligations [Line Items]
Maximum Potential Future Payments	9
Other Guarantees [Member]
Guarantor Obligations [Line Items]
Carrying Amount	162	$ 184
Maximum Potential Future Payments	$ 867

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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- Definition

Guarantee obligations collateral held.

+ References

No definition available.

+ Details

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Period Type:	instant

- Details

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- Details

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- Details

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- Details

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- Details

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