CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) (USD $)	0 Months Ended	6 Months Ended
Aug. 01, 2013	Jun. 30, 2013
Income Statement [Abstract]
Dividends Declared per Share of Common Stock, special dividend (in dollars per share)	$ 0.28	$ 0.50

Represents the special dividend declared during the period for each share of common stock outstanding with cash dividends.

No definition available.

Name:	mfa_CommonStockSpecialDividendsPerShareDeclared
Namespace Prefix:	mfa_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration