Represents the maximum percentage of certain compensation that may be deferred by the senior officers and non-employee directors pursuant to Deferred Plans.

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

- Definition

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

+ Details

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

- Definition

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

+ Details

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

- Definition

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

+ Details

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

- Definition

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

+ Details

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

- Definition

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

+ Details

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

- Definition

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

+ Details

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

- Definition

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

+ References

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

+ Details

Name:	us-gaap_DeferredCompensationArrangementWithIndividualCompensationExpense
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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.

+ Details

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

- Definition

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.

+ References

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

+ Details

Name:	us-gaap_DeferredCompensationArrangementWithIndividualRecordedLiability
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

Name:	us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Equity Compensation, Employment Agreements and Other Benefit Plans (Details 2) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Deferred Compensation Plans
Deferred compensation activity
Deferrable compensation by the employee, maximum (as a percent)			100.00%
Expenses related to Deferred Plans	$ (21,000)	$ 20,000	$ (18,000)	$ 43,000
Undistributed income deferred	164,000		164,000		266,000
Liability under deferred plans	197,000		197,000		433,000
Deferred Compensation Plans \| Non-employee directors
Deferred compensation activity
Expenses related to Deferred Plans	(21,000)	19,000	(17,000)	40,000
Undistributed income deferred	164,000		164,000		253,000
Liability under deferred plans	197,000		197,000		405,000
Deferred Compensation Plans \| Officers
Deferred compensation activity
Expenses related to Deferred Plans		1,000	(1,000)	3,000
Undistributed income deferred					13,000
Liability under deferred plans					28,000
Savings Plan
Deferred compensation activity
Employer contribution percentage on first 3 percent of eligible compensation deferred by employees			100.00%
Percentage of eligible compensation deferred by employees qualifying for 100 percent matching contribution			3.00%
Employer contribution percentage on next 2 percent of eligible compensation deferred by employees			50.00%
Percentage of eligible compensation deferred by employees qualifying for 50 percent matching contribution			2.00%
Percentage of employer matching contributions that vest immediately			100.00%
Expenses for matching contributions	$ 43,000	$ 40,000	$ 128,000	$ 120,000