XML 23 R70.htm IDEA: XBRL DOCUMENT v2.4.1.9
Equity Compensation, Employment Agreements and Other Benefit Plans (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Share based compensation      
Maximum shares authorized for grant 13,500,000.0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized    
Shares available for grant 9,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant    
Accrued Dividends Payable $ 74,529,000us-gaap_DividendsPayableCurrentAndNoncurrent $ 73,643,000us-gaap_DividendsPayableCurrentAndNoncurrent $ 72,222,000us-gaap_DividendsPayableCurrentAndNoncurrent
Expense related to equity-based compensation instruments 8,585,000us-gaap_AllocatedShareBasedCompensationExpense 4,158,000us-gaap_AllocatedShareBasedCompensationExpense 6,488,000us-gaap_AllocatedShareBasedCompensationExpense
DER      
Share based compensation      
Payments attributable to DERs 748,000mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardDividendEquivalentRightsPayment
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
2,100,000mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardDividendEquivalentRightsPayment
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
1,500,000mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardDividendEquivalentRightsPayment
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
Special cash dividends paid (in dollars per share)   $ 0.78mfa_CommonStockSpecialDividendsPerShareDeclared
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
 
Special cash dividends paid, amount   996,000mfa_CommonStockSpecialDividendsDeclared
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
 
Average forfeiture rate assumed on DERs outstanding 0.00%mfa_ForfeitureRateAssumedonDERsOutstanding
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
   
Weighted average period over which DERs are scheduled to elapse 1 year 7 months 24 days    
Expense related to equity-based compensation instruments 146,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
195,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
237,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
Activity and related information      
Outstanding at beginning of year (in shares) 851,328us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
1,280,898us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
1,655,848us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
Granted (in shares) 630,815us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
40,324us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
21,938us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
Cancelled, forfeited or expired (263,669)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
(469,894)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
(396,888)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
Outstanding at end of year (in shares) 1,218,474us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
851,328us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
1,280,898us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
Weighted Average Grant Date Fair Value      
Outstanding at beginning of year (in dollars per share) $ 5.95mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
$ 7.08mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
$ 7.35mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
Granted (in dollars per share) $ 6.64us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
$ 9.14us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
$ 8.17us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
Cancelled/forfeited (in dollars per share) $ 3.80us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
$ 9.32us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
$ 8.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
Outstanding at end of year (in dollars per share) $ 3.33mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
$ 5.95mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
$ 7.08mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_DividendEquivalentRightsMember
Stock options      
Share based compensation      
Period to determine market value of the common stock to qualify as an incentive stock option for tax purposes 1 year    
Maximum grant date market value of the common stock to be received upon exercise of options in one calendar year 100,000mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsMaximumMarketValueOfExercisesInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
   
Exercise price of an ISO relative to fair market value on the grant date, minimum (as a percent) 100.00%mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisePriceAsPercentageOfCommonStockFairMarketValue
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
   
Exercise price of an ISO granted to a 10% stockholder relative to fair market value on the grant date, minimum (as a percent) 110.00%mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisePriceForISOGrantedTo10PercentShareholderAsPercentageOfCommonStockFairMarketValue
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
   
Percentage of stockholders to whom 110% of ISO is granted 10.00%mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsPercentageOfShareholdersToWhom110PercentOfISOIsGranted
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
   
Maximum period for exercise of stock options 10 years    
Aggregate intrinsic value of total stock options Outstanding 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
   
Intrinsic value of options exercised   19,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
6,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Stock options activity      
Outstanding at beginning of year (in shares) 5,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
427,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
482,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Granted (in shares) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Cancelled, forfeited or expired (in shares) (5,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
(402,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
(50,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Exercised (in shares) 0us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
(20,000)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
(5,000)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Outstanding at end of year (in shares) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
5,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
427,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Options exercisable at end of year (in shares) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
5,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
427,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Weighted Average Exercise Price      
Outstanding at beginning of year (in dollars per share) $ 8.40us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 10.14us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 10.12us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Granted (in dollars per share) $ 0.00us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 0.00us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 0.00us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Cancelled, forfeited or expired (in dollars per share) $ 8.40us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 10.25us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 10.25us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Exercised (in dollars per share) $ 0.00us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 8.40us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 6.99us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Outstanding at end of year (in dollars per share) $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 8.40us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 10.14us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Options exercisable at end of year (in dollars per share) $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 8.40us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 10.14us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Restricted Stock      
Share based compensation      
Unrecognized compensation cost 1,800,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
3,300,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
 
Accrued Dividends Payable 354,000us-gaap_DividendsPayableCurrentAndNoncurrent
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
413,000us-gaap_DividendsPayableCurrentAndNoncurrent
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
 
Total fair value of stock vested 5,700,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
2,100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
5,100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
Period for recognizing unrecognized compensation cost 2 years 1 month 13 days    
Expense related to equity-based compensation instruments 5,553,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
2,150,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
5,102,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
Activity and related information      
Outstanding at beginning of year (in shares) 443,967us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
483,442us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
752,155us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
Granted (in shares) 491,797us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
231,531us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
418,184us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
Vested (in shares) (690,397)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
(270,456)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
(685,864)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
Cancelled, forfeited or expired (1,419)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
(550)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
(1,033)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
Outstanding at end of year (in shares) 243,948us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
443,967us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
483,442us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
Weighted Average Grant Date Fair Value      
Outstanding at beginning of year (in dollars per share) $ 7.50mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
$ 7.74mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
$ 7.33mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
Granted (in dollars per share) $ 8.29us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
$ 7.33us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
$ 7.99us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
Vested (in dollars per share) $ 8.07us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
$ 7.77us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
$ 7.45us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
Cancelled/forfeited (in dollars per share) $ 7.58us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
$ 7.72us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
$ 6.91us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
Outstanding at end of year (in dollars per share) $ 7.48mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
$ 7.50mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
$ 7.74mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
Restricted Stock Units      
Share based compensation      
Unrecognized compensation cost 2,800,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
1,600,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
 
Period for recognizing unrecognized compensation cost 1 year 11 months 5 days    
Weighted average forfeiture rate of unvested RSUs (as a percent) 0.00%mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardWeightedAverageForfeitureRatePercent
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
   
Expense related to equity-based compensation instruments 2,886,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
1,813,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
1,149,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Activity and related information      
Outstanding at beginning of year (in shares) 777,818us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
727,648us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
978,848us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Granted (in shares) 630,815us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
112,824us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
94,438us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Settled (in shares) (87,338)mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
(53,091)mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
(297,775)mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Cancelled, forfeited or expired (102,821)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
(9,563)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
(47,863)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Outstanding at end of year (in shares) 1,218,474us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
777,818us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
727,648us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Vested but not settled at end of year 643,138mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNumberVested
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
98,824mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNumberVested
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
43,875mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNumberVested
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Unvested at end of period (in shares) 575,336us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
678,994us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
683,773us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Weighted Average Grant Date Fair Value      
Outstanding at beginning of year (in dollars per share) $ 6.48mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 6.43mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 7.18mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Granted (in dollars per share) $ 6.64us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 5.82us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 4.80us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Settled (in dollars per share) $ 6.86mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 4.15mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 8.57mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Cancelled/forfeited (in dollars per share) $ 2.90us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 7.88us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 5.30us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Outstanding at end of year (in dollars per share) $ 6.84mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 6.48mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 6.43mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Vested but not settled at end of year (in dollars per share) $ 7.10mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValueVested
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 7.93mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValueVested
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 6.74mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValueVested
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Unvested at end of year (in dollars per share) $ 6.54us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 6.27us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
$ 6.41us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
Restricted Stock Units | Chief Executive Officer      
Share based compensation      
Expense related to equity-based compensation instruments $ 500,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
/ us-gaap_TitleOfIndividualAxis
= us-gaap_ChiefExecutiveOfficerMember
   
RSUs with Service Condition      
Activity and related information      
Outstanding at beginning of year (in shares) 490,099us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
448,141us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
722,132us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
Granted (in shares) 357,015us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
64,483us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
38,784us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
Settled (in shares) (72,873)mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
(21,025)mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
(297,775)mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
Cancelled, forfeited or expired (5,067)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
(1,500)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
(15,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
Outstanding at end of year (in shares) 769,174us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
490,099us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
448,141us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
Vested but not settled at end of year 467,638mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNumberVested
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
84,199mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNumberVested
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
29,250mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNumberVested
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
Unvested at end of period (in shares) 301,536us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
405,900us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
418,891us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
Weighted Average Grant Date Fair Value      
Outstanding at beginning of year (in dollars per share) $ 7.75mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
$ 7.61mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
$ 8.04mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
Granted (in dollars per share) $ 7.22us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
$ 8.23us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
$ 7.01us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
Settled (in dollars per share) $ 7.28mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
$ 6.20mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
$ 8.57mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
Cancelled/forfeited (in dollars per share) $ 7.36us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
$ 7.77us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
$ 7.77us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
Outstanding at end of year (in dollars per share) $ 7.55mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
$ 7.75mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
$ 7.61mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
Vested but not settled at end of year (in dollars per share) $ 7.81mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValueVested
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
$ 8.50mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValueVested
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
$ 7.77mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValueVested
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
Unvested at end of year (in dollars per share) $ 7.15us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
$ 7.60us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
$ 7.60us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithServiceConditionsMember
RSUs with Market and Service Conditions      
Activity and related information      
Outstanding at beginning of year (in shares) 287,719us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
279,507us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
256,716us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
Granted (in shares) 273,800us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
48,341us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
55,654us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
Settled (in shares) (14,465)mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
(32,066)mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
0mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
Cancelled, forfeited or expired (97,754)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
(8,063)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
(32,863)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
Outstanding at end of year (in shares) 449,300us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
287,719us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
279,507us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
Vested but not settled at end of year 175,500mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNumberVested
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
14,625mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNumberVested
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
14,625mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNumberVested
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
Unvested at end of period (in shares) 273,800us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
273,094us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
264,882us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
Weighted Average Grant Date Fair Value      
Outstanding at beginning of year (in dollars per share) $ 4.32mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
$ 4.55mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
$ 4.78mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
Granted (in dollars per share) $ 5.87us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
$ 2.59us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
$ 3.26us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
Settled (in dollars per share) $ 4.71mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
$ 2.80mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
$ 0.00mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
Cancelled/forfeited (in dollars per share) $ 2.67us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
$ 7.89us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
$ 4.17us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
Outstanding at end of year (in dollars per share) $ 5.61mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
$ 4.32mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
$ 4.55mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
Vested but not settled at end of year (in dollars per share) $ 5.21mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValueVested
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
$ 4.69mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValueVested
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
$ 4.69mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsWeightedAverageGrantDateFairValueVested
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
Unvested at end of year (in dollars per share) $ 5.87us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
$ 4.30us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
$ 4.54us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= mfa_RestrictedStockUnitsRSUWithMarketAndServiceConditionsMember
RSUs with Service Condition and both Service and Market Conditions      
Activity and related information      
Granted (in shares) 547,600us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RSUsWithServiceConditionAndBothServiceAndMarketConditionsMember
   
Fair value assumptions      
Weighted average volatility estimated (as a percent) 22.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageVolatilityRate
/ us-gaap_AwardTypeAxis
= mfa_RSUsWithServiceConditionAndBothServiceAndMarketConditionsMember
23.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageVolatilityRate
/ us-gaap_AwardTypeAxis
= mfa_RSUsWithServiceConditionAndBothServiceAndMarketConditionsMember
23.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageVolatilityRate
/ us-gaap_AwardTypeAxis
= mfa_RSUsWithServiceConditionAndBothServiceAndMarketConditionsMember
Expected term 3 years 3 years 3 years
Weighted average risk-free rate (as a percent)   0.65%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= mfa_RSUsWithServiceConditionAndBothServiceAndMarketConditionsMember
0.41%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= mfa_RSUsWithServiceConditionAndBothServiceAndMarketConditionsMember
Estimated annual dividend yield (as a percent) 8.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= mfa_RSUsWithServiceConditionAndBothServiceAndMarketConditionsMember
13.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= mfa_RSUsWithServiceConditionAndBothServiceAndMarketConditionsMember
12.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= mfa_RSUsWithServiceConditionAndBothServiceAndMarketConditionsMember
RSUs with Service Condition and both Service and Market Conditions | Minimum      
Fair value assumptions      
Weighted average risk-free rate (as a percent) 0.73%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= mfa_RSUsWithServiceConditionAndBothServiceAndMarketConditionsMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
   
RSUs with Service Condition, weighted average grant date fair value based on share closing price      
Activity and related information      
Granted (in shares) 83,215us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= mfa_RSUsWithServiceConditionWeightedAverageGrantDateFairValueBasedonShareClosingPriceMember
   
RSUs with Service Condition, weighted average grant date fair value based on share closing price | Minimum      
Fair value assumptions      
Common stock, closing price (in dollars per share) $ 7.19us-gaap_SharePrice
/ us-gaap_AwardTypeAxis
= mfa_RSUsWithServiceConditionWeightedAverageGrantDateFairValueBasedonShareClosingPriceMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
   
RSUs with Service Condition, weighted average grant date fair value based on share closing price | Maximum      
Fair value assumptions      
Common stock, closing price (in dollars per share) $ 8.16us-gaap_SharePrice
/ us-gaap_AwardTypeAxis
= mfa_RSUsWithServiceConditionWeightedAverageGrantDateFairValueBasedonShareClosingPriceMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
   
2010 Equity Compensation Plan      
Share based compensation      
Maximum number of common shares that can be granted to participant in any one year 1,500,000mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerParticipant
/ us-gaap_PlanNameAxis
= mfa_EquityCompensationPlan2010Member
   
Period during which a participant can be awarded the maximum number of shares allowable under the Plan 1 year    
Maximum percentage of common shares that can be owned or deemed to be owned by a participant (more than) 9.80%mfa_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumPercentageOfSharesPerParticipant
/ us-gaap_PlanNameAxis
= mfa_EquityCompensationPlan2010Member