Name:	mfa_DeferredCompensationArrangementWithIndividualCompensationDeferrablePercentageMaximum
Namespace Prefix:	mfa_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The compensation expense net of market fluctuations recognized during the period pertaining to the deferred compensation arrangement.

No definition available.

Name:	mfa_DeferredCompensationArrangementWithIndividualCompensationExpenseNetOfMarketFluctuations
Namespace Prefix:	mfa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the percentage of the employer's matching contribution on the first tier of eligible compensation deferred by employees.

No definition available.

Name:	mfa_DeferredCompensationArrangementWithIndividualEmployerMatchingContributionOnFirstTierOfEligibleCompensation
Namespace Prefix:	mfa_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the percentage of the employer's matching contribution on the second tier of eligible compensation deferred by employees.

No definition available.

Name:	mfa_DeferredCompensationArrangementWithIndividualEmployerMatchingContributionOnSecondTierOfEligibleCompensation
Namespace Prefix:	mfa_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the percentage of the first tier of eligible compensation deferred by employees and receiving the highest level of employer match.

No definition available.

Name:	mfa_DeferredCompensationArrangementWithIndividualPercentageOfFirstEligibleCompensationForEmployerContributionMatch
Namespace Prefix:	mfa_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the percentage of the second tier of eligible compensation deferred by employees and receiving the second level of employer match.

No definition available.

Name:	mfa_DeferredCompensationArrangementWithIndividualPercentageOfNextEligibleCompensationForEmployerContributionMatch
Namespace Prefix:	mfa_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents undistributed income deferred by participants under a deferred compensation arrangement as of the balance sheet date.

No definition available.

Name:	mfa_DeferredCompensationArrangementWithIndividualUndistributedIncomeDeferred
Namespace Prefix:	mfa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The percentage of employer matching contributions under a deferred compensation arrangement that vest immediately.

No definition available.

Name:	mfa_MatchingContributionByEmployerVestingPercent
Namespace Prefix:	mfa_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The compensation expense recognized during the period pertaining to the deferred compensation arrangement.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 710

-SubTopic 10

-Section 30

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64, 65

-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 AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 12

-Paragraph 6, 7

-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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

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

The amount of distributions made to the individual during the period.

No definition available.

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

The amount of payment into the fund established for purposes of making future disbursements to the individual in accordance with the terms and understanding of the deferred compensation arrangement.

No definition available.

Name:	us-gaap_DeferredCompensationArrangementWithIndividualEmployerContribution
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The carrying amount of the liability as of the balance sheet date to an individual under a deferred compensation arrangement. This amount may be the result of periodic accruals made over the period of active employment, or reflect termination benefits resulting contractual terms or a death benefit.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64, 65

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 12

-Paragraph 6, 7

-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

-Topic 710

-SubTopic 10

-Section 30

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363