Name:	mfa_AvailableForSaleSecuritiesChangesInPurchaseDiscountDueToNetImpairmentLossesRecognizedInEarnings
Namespace Prefix:	mfa_
Data Type:	xbrli:monetaryItemType
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Represents the changes in the purchase discount on available-for-sale securities due to purchases during the period.

No definition available.

Name:	mfa_AvailableForSaleSecuritiesChangesInPurchaseDiscountDueToPurchases
Namespace Prefix:	mfa_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

Represents the changes in the purchase discount on available-for-sale securities due to sales during the period.

No definition available.

Name:	mfa_AvailableForSaleSecuritiesChangesInPurchaseDiscountDueToSales
Namespace Prefix:	mfa_
Data Type:	xbrli:monetaryItemType
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Available For Sale Securities, Changes in Purchase Discount Due to Settlements

No definition available.

Name:	mfa_AvailableForSaleSecuritiesChangesinPurchaseDiscountDuetoSettlements
Namespace Prefix:	mfa_
Data Type:	xbrli:monetaryItemType
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Represent the total amount of purchase discount related to available-for-sale securities.

No definition available.

Name:	mfa_AvailableForSaleSecuritiesDiscount
Namespace Prefix:	mfa_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Represent the amount of purchase discount on available-for-sale securities designated as credit reserves reallocated during the period to accretable purchase discount.

No definition available.

Name:	mfa_AvailableForSaleSecuritiesPurchaseDiscountDesignatedAsCreditReservesReallocatedToAccretablePurchaseDiscount
Namespace Prefix:	mfa_
Data Type:	xbrli:monetaryItemType
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-- None. No documentation exists for this element. --

No definition available.

Name:	mfa_AvailableForSaleSecuritiesPurchaseDiscountRollforward
Namespace Prefix:	mfa_
Data Type:	xbrli:stringItemType
Balance Type:	na
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Amount of accretion of purchase discount on nonoperating securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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The amount of other than temporary impairment losses on investments in debt and equity securities categorized as Available-for-sale which have been recognized in earnings during the period. Such impairment losses consist of other than temporary impairments (OTTI) on equity securities, credit losses on investments in debt securities, and when the entity intends to sell an impaired debt security or it is more likely than not that the entity will be required to sell the impaired debt security before recovery of its amortized cost basis.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 8A
-URI http://asc.fasb.org/extlink&oid=82896770&loc=SL6284422-111562

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

Cash received for the settlement of litigation during the current period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585

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Period Type:	duration

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Namespace Prefix:
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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_InvestmentSecondaryCategorizationAxis=mfa_AccretableDiscountMember
Namespace Prefix:
Data Type:	na
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Period Type:

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Namespace Prefix:
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