Derivative Financial Instruments - Narrative (Details) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2017 USD ($) security	Dec. 31, 2016 USD ($)
Derivative [Line Items]
Cash collateral received for derivative instruments	$ 1,700	$ 1,990
Cash collateral provided for derivative instruments	742	4,390
Fair value of derivative liabilities	$ 9,394	$ 16,684
Weighted average life of trusts	4 years 4 months 24 days	4 years 6 months
Credit swap agreements
Derivative [Line Items]
Fair value of derivative liabilities	$ 1,140
Fair value of collateral posted	25
Maximum additional amount of payments related to termination events	$ 1,110
Interest rate swap \| Fair Value Hedges \| Senior notes
Derivative [Line Items]
Number of securities \| security	8
Interest rate swap \| Fair Value Hedges \| Subordinated note
Derivative [Line Items]
Number of securities \| security	1

Cash Collateral Provided For Derivative Instruments

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- Definition

Cash Collateral Received For Derivative Instruments

+ References

No definition available.

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- Definition

Weighted Average Life Of Trusts

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- Definition

The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624258-113959

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- Definition

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
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-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624258-113959

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- Definition

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

+ References

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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.

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- Definition

The number of derivative instruments of a particular group held by the entity.

+ References

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