Name:	agnc_AgencySecuritiesAmortizedCost
Namespace Prefix:	agnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

This item represents the gross unrealized gains for agency securities, at a point in time.

No definition available.

Name:	agnc_AgencySecuritiesGrossUnrealizedGain
Namespace Prefix:	agnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

This item represents the gross unrealized losses for agency securities, at a point in time.

No definition available.

Name:	agnc_AgencySecuritiesPledgedAsCollateralGrossUnrealizedLoss
Namespace Prefix:	agnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

CMO and Interest Only and Pricincipal Only Securities, Maximum Loss Exposure

No definition available.

Name:	agnc_CmoAndInterestOnlyPricincipalOnlySecuritiesMaximumLossExposure
Namespace Prefix:	agnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Interest Rate Derivative Assets at Amortized Cost

No definition available.

Name:	agnc_InterestRateDerivativeAssetsAtAmortizedCost
Namespace Prefix:	agnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Prepayment Rate Of Remaining Life Of Investment Portfolio

No definition available.

Name:	agnc_PrepaymentRateOfRemainingLifeOfInvestmentPortfolio
Namespace Prefix:	agnc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents total investment in agency securities at fair value.

No definition available.

Name:	agnc_TotalAgencySecurities
Namespace Prefix:	agnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Unrealized Gain on Derivatives

No definition available.

Name:	agnc_UnrealizedGainOnDerivatives
Namespace Prefix:	agnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Unrealized Loss on Derivatives

No definition available.

Name:	agnc_UnrealizedLossOnDerivatives
Namespace Prefix:	agnc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7534914&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Available-for-Sale Securities

-URI http://asc.fasb.org/extlink&oid=6505594

Name:	us-gaap_AvailableForSaleSecuritiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.