Participating Securities, Distributed And Undistributed Earnings (Loss), Basic And Diluted

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

- Definition

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

EPS Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Basic (Loss)/Earnings per Share:
Net (loss)/income	$ (55,018)	$ (100,367)	$ (82,906)	$ 132,511	$ 66,714	$ 85,522	$ (238,291)	$ 284,747
Dividends declared on preferred stock	(8,218)			(8,218)			(24,656)	(24,656)
Dividends, dividend equivalents and undistributed earnings allocated to participating securities	(174)			(435)			(489)	(915)
Net (loss)/income to available common stockholders - basic	$ (63,410)			$ 123,858			$ (263,436)	$ 259,176
Basic weighted average common shares outstanding (in shares)	101,795			110,222			103,609	111,120
Basic (Loss)/Earnings per Share (in dollars per share)	$ (0.62)			$ 1.12			$ (2.54)	$ 2.33
Diluted (Loss)/Earnings per Share:
Net (loss)/income to available common stockholders - basic	$ (63,410)			$ 123,858			$ (263,436)	$ 259,176
Interest expense on Convertible Senior Notes	0			3,920			0	11,743
Dividends, dividend equivalents and undistributed earnings allocated to participating securities	0			435			0	915
Net (loss)/income available to common stockholders - diluted	$ (63,410)			$ 128,213			$ (263,436)	$ 271,834
Basic weighted average common shares outstanding (in shares)	101,795			110,222			103,609	111,120
Effect of assumed Convertible Senior Notes conversion to common shares (in shares)	0			7,230			0	7,230
Unvested and vested restricted stock units (in shares)	0			1,064			0	640
Diluted weighted average common shares outstanding (in shares)	101,795			118,516			103,609	118,990
Diluted (Loss)/Earnings per Common Share (in dollars per share)	$ (0.62)			$ 1.08			$ (2.54)	$ 2.28
Anti-dilutive securities excluded from diluted earnings per share calculations (in shares)							1,100
RSUs
Diluted (Loss)/Earnings per Share:
Weighted average grant date fair value (in dollars per share)	$ 18.03						$ 18.03