Pledged Assets (Assets Pledged from Counterparties) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Offsetting Assets and Liabilities [Line Items]
Federal Home Loan Bank Stock		$ 126
Available-for-sale Securities Pledged as Collateral	$ 41,263	43,943
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	7,221	7,636
Restricted Cash and Cash Equivalents	261	74
Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	0	14
Restricted Cash and Cash Equivalents	0	107
Restricted Cash and Securities Pledged	7,315	7,757
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	0	14
Securities Sold under Agreements to Repurchase [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	0	14
Derivative [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	0	0
Restricted Cash and Securities Pledged	0	107
US Treasury Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral		173
US Treasury Securities [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	7,315	7,636
Reverse Repurchase Agreements [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	7,315	7,636
Reverse Repurchase Agreements [Member] \| US Treasury Securities [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	7,315	7,636
Derivative [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	287	275
Restricted Cash and Cash Equivalents	238	14
Derivative [Member] \| US Treasury Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral		0
Derivative [Member] \| US Treasury Securities [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	0	0
Derivative [Member] \| Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted Cash and Cash Equivalents	$ 0	$ 107

Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value

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- Definition

[Line Items] for Offsetting Assets and Liabilities [Table]

+ References

No definition available.

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- Definition

Restricted Cash and Securities Pledged

+ References

No definition available.

+ Details

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- Definition

The fair value of available-for-sale securities that serve as collateral for borrowings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5086-111524

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- Definition

Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 325
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6478792&loc=d3e63345-112809

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- Definition

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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