Derivative Instruments and Other Financial Instruments Used For Hedging - Derivatives Designated as Cash Flow Hedges (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Cash Flow Hedges \| Interest rate contracts
Amount and location of net gains and losses
Amount of Gain (Loss) Recognized in OCI on Derivative Instruments (Effective Portion)		$ 126
Cash Flow Hedges \| Interest rate contracts \| Interest income
Amount and location of net gains and losses
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	$ 168	115
Cash Flow Hedges \| Interest rate contracts \| Interest expense
Amount and location of net gains and losses
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	2	2
Cash Flow Hedges \| Interest rate contracts \| Noninterest expense
Amount and location of net gains and losses
Gain (Loss) Recognized in Income on Derivative Instruments (Ineffective Portion)	1	2
Cash Flow Hedges \| Interest rate contracts \| Noninterest expense \| Maximum
Amount and location of net gains and losses
Gain (Loss) Recognized in Income on Derivative Instruments (Ineffective Portion)	3	(1)
Designated as hedging instrument \| Fair Value Hedging
Amount and location of net gains and losses
Derivative	2	2
Hedged Item	(2)	(1)
Hedge Ineffectiveness	0	1
Designated as hedging instrument \| Fair Value Hedging \| Interest rate contracts
Amount and location of net gains and losses
Derivative	2	2
Hedged Item	(2)	(1)
Hedge Ineffectiveness	0	1
Designated as hedging instrument \| Cash Flow Hedges
Amount and location of net gains and losses
Amount of Gain (Loss) Recognized in OCI on Derivative Instruments (Effective Portion)	195	126
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	170	117
Gain (Loss) Recognized in Income on Derivative Instruments (Ineffective Portion)	1	$ 2
Designated as hedging instrument \| Cash Flow Hedges \| Interest rate contracts
Amount and location of net gains and losses
Amount of Gain (Loss) Recognized in OCI on Derivative Instruments (Effective Portion)	$ 195

Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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+ References

No definition available.

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The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624177-113959

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- Definition

The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1),(2)
-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

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Amount of gain (loss)recognized in the income statement from the hedging ineffectiveness of a fair value hedge.

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Total amount of gain (loss) derived from fair value hedges recognized in earnings in the period.

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