Derivative Financial Instruments and Hedging Activities (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Designated as Hedging Instrument [Member] \| Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	$ 7,417	$ 3,070
Derivative asset, Fair value	92	12
Designated as Hedging Instrument [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Notional amount	7,860	8,991
Derivative liability, Fair value	260	310
Designated as Hedging Instrument [Member] \| Fair Value Hedging [Member] \| Other Assets [Member] \| Interest Rate Swaps [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	3,500	0
Derivative asset, Fair value	20	0
Designated as Hedging Instrument [Member] \| Fair Value Hedging [Member] \| Other Liabilities [Member] \| Interest Rate Swaps [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Notional amount	7,860	7,700
Derivative liability, Fair value	260	276
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Other Assets [Member] \| Interest Rate Swaps [Member] \| Level 2,3 [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	2,561	3,070
Derivative asset, Fair value	12	12
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Other Assets [Member] \| Foreign Currency Swaps [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	1,356	0
Derivative asset, Fair value	60	0
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Other Liabilities [Member] \| Interest Rate Swaps [Member] \| Level 2,3 [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Notional amount	0	500
Derivative liability, Fair value	0	1
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Other Liabilities [Member] \| Foreign Currency Swaps [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Notional amount	0	791
Derivative liability, Fair value	0	33
Not Designated as Hedging Instrument [Member] \| Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	51,210	17,657
Derivative asset, Fair value	251	80
Not Designated as Hedging Instrument [Member] \| Other Assets [Member] \| Interest Rate Swaps [Member] \| Level 2,3 [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	33,218	7,959
Derivative asset, Fair value	123	54
Not Designated as Hedging Instrument [Member] \| Other Assets [Member] \| Interest Rate Caps and Floors [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	16,810	9,698
Derivative asset, Fair value	43	26
Not Designated as Hedging Instrument [Member] \| Other Assets [Member] \| Foreign Currency Swaps [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, Notional amount	1,182	0
Derivative asset, Fair value	85	0
Not Designated as Hedging Instrument [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Notional amount	31,290	18,316
Derivative liability, Fair value	102	54
Not Designated as Hedging Instrument [Member] \| Other Liabilities [Member] \| Interest Rate Swaps [Member] \| Level 2,3 [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Notional amount	12,823	6,170
Derivative liability, Fair value	59	28
Not Designated as Hedging Instrument [Member] \| Other Liabilities [Member] \| Interest Rate Caps and Floors [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Notional amount	18,467	12,146
Derivative liability, Fair value	43	26
Not Designated as Hedging Instrument [Member] \| Other Liabilities [Member] \| Foreign Currency Swaps [Member] \| Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Notional amount	0	0
Derivative liability, Fair value	$ 0	$ 0

Nominal or face amount used to calculate payments on the derivative asset.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5579245-113959

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-Publisher FASB
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Fair value, after the effects of master netting arrangements, of a financial asset or other 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 assets not subject to a master netting arrangement and not elected to be offset.

+ References

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-Publisher FASB
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition

Nominal or face amount used to calculate payments on the derivative liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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+ References

No definition available.

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