Equity Compensation and Other Benefit Plans - Savings Plan (Details) - Savings Plan - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Share based compensation
Employer contribution percentage on first 3 percent of eligible compensation deferred by employees (percent)	100.00%
Percentage of eligible compensation deferred by employees qualifying for 100 percent matching contribution (percent)	3.00%
Employer contribution percentage on next 2 percent of eligible compensation deferred by employees (percent)	50.00%
Percentage of eligible compensation deferred by employees qualifying for 50 percent matching contribution (percent)	2.00%
Percentage of employer matching contributions that vest immediately (percent)	100.00%
Expenses for matching contributions	$ 316	$ 125

- Definition

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

+ References

No definition available.

+ Details

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Namespace Prefix:	mfa_
Data Type:	dtr-types:percentItemType
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Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

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Namespace Prefix:	mfa_
Data Type:	dtr-types: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.

+ References

No definition available.

+ Details

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Namespace Prefix:	mfa_
Data Type:	dtr-types: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.

+ References

No definition available.

+ Details

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Namespace Prefix:	mfa_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	mfa_MatchingContributionByEmployerVestingPercent
Namespace Prefix:	mfa_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of contributions made by employer into fund established for purposes of making future disbursement to individual in accordance with deferred compensation arrangement.

+ References

No definition available.

+ Details

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

- 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.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
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- Details

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