Equity - Quarterly Dividends Paid by Farmer Mac (Details) - $ / shares	3 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Series A
Class of Stock [Line Items]
Preferred stock dividends (in dollars per share)	$ 0	$ 0.2530	$ 0.3672	$ 0.3672	$ 0.3672	$ 0.3672	$ 0.3672	$ 0.3672	$ 0.3672	$ 0.3672	$ 0.3672	$ 0.3672
Series C
Class of Stock [Line Items]
Preferred stock dividends (in dollars per share)	0.3750	0.3750	0.3750	0.3750	0.3750	0.3750	0.3750	0.3750	0.3750	0.3750	0.3750	0.3750
Series D
Class of Stock [Line Items]
Preferred stock dividends (in dollars per share)	0.3563	0.3563	0.3563	0.3563	0.3563	0.3563	0.2533	0
Series D | May 13, 2019 to July 17, 2019
Class of Stock [Line Items]
Preferred stock dividends (in dollars per share)							0.2533
Series E
Class of Stock [Line Items]
Preferred stock dividends (in dollars per share)	0.3594	0.3594	0.2276	0
Series E | May 20, 2020 to July 17, 2020
Class of Stock [Line Items]
Preferred stock dividends (in dollars per share)			0.2276
Series E | July 17, 2020 to September 19, 2020
Class of Stock [Line Items]
Preferred stock dividends (in dollars per share)		0.2530
Series F
Class of Stock [Line Items]
Preferred stock dividends (in dollars per share)	$ 0.3281	0.2078	$ 0	$ 0
Series F | August 20, 2020 to October 17, 2020
Class of Stock [Line Items]
Preferred stock dividends (in dollars per share)		$ 0.2078
Series B
Class of Stock [Line Items]
Preferred stock dividends (in dollars per share)					$ 0	$ 0	0.2626	$ 0.4297	$ 0.4297	$ 0.4297	$ 0.4297	$ 0.4297
Series B | April 17, 2019 to June 12, 2019
Class of Stock [Line Items]
Preferred stock dividends (in dollars per share)							$ 0.2626