Investment Securities Investment Securities (Summary of Investment in Agency Security) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	$ 73,828	$ 98,670
Debt Securities, Trading and Available-for-sale	77,143	100,442
Total agency MBS, at fair value	75,832	98,887
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	221	198
Debt Securities, Trading and Available-for-sale	222	209
Commercial Mortgage Backed Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	361	352
Debt Securities, Trading and Available-for-sale	377	370
Credit Risk Transfer Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	742	961
Debt Securities, Trading and Available-for-sale	712	976
Fixed Income Securities [Member] \| Agency Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	71,885	96,375
Debt Securities, Trading and Available-for-sale	75,165	98,074
Adjustable-Rate [Member] \| Agency Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	109	160
Debt Securities, Trading and Available-for-sale	112	163
Collateralized Mortgage Obligations [Member] \| Agency Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	365	441
Debt Securities, Trading and Available-for-sale	381	447
Multifamily [Member] \| Agency Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	17	37
Debt Securities, Trading and Available-for-sale	19	39
Interest Only And Principal Only Strip [Member] \| Agency Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	128	146
Debt Securities, Trading and Available-for-sale	155	164
Agency Securities [Member]
Debt and Equity Securities, FV-NI [Line Items]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	$ 72,504	$ 97,159

Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) at cost.

No definition available.

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- Definition

Represents total investment in agency securities at fair value.

+ References

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- Definition

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121553693&loc=d3e26610-111562

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+ References

No definition available.

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