Guarantees and Commitments - Unpaid Principal Balances by Delinquency Status (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Guarantor Obligations [Line Items]
Total	$ 7,758,286	$ 7,261,933
Current
Guarantor Obligations [Line Items]
Total	8,876,515	8,315,566
Total Past Due
Guarantor Obligations [Line Items]
Total	6,482	6,286
30-59 Days
Guarantor Obligations [Line Items]
Total	2,345	4,582
60-89 Days
Guarantor Obligations [Line Items]
Total	482	632
90 Days and Greater
Guarantor Obligations [Line Items]
Total	3,655	1,072
Farm & Ranch
Guarantor Obligations [Line Items]
Total	6,777,749	6,176,438
Farm & Ranch | Current
Guarantor Obligations [Line Items]
Total	6,633,343	6,055,154
Farm & Ranch | Total Past Due
Guarantor Obligations [Line Items]
Total	6,482	6,286
Farm & Ranch | 30-59 Days
Guarantor Obligations [Line Items]
Total	2,345	4,582
Farm & Ranch | 60-89 Days
Guarantor Obligations [Line Items]
Total	482	632
Farm & Ranch | 90 Days and Greater
Guarantor Obligations [Line Items]
Total	3,655	1,072
Rural Utilities
Guarantor Obligations [Line Items]
Total	2,243,172	2,260,412
Rural Utilities | Current
Guarantor Obligations [Line Items]
Total	2,243,172	2,260,412
Rural Utilities | Total Past Due
Guarantor Obligations [Line Items]
Total	0	0
Rural Utilities | 30-59 Days
Guarantor Obligations [Line Items]
Total	0	0
Rural Utilities | 60-89 Days
Guarantor Obligations [Line Items]
Total	0	0
Rural Utilities | 90 Days and Greater
Guarantor Obligations [Line Items]
Total	0	0
LTSPCs and Farmer Mac Guaranteed Securities | Farm & Ranch
Guarantor Obligations [Line Items]
Total	2,667,610	2,404,743
LTSPCs and Farmer Mac Guaranteed Securities | Farm & Ranch | Current
Guarantor Obligations [Line Items]
Total	2,659,372	2,389,777
LTSPCs and Farmer Mac Guaranteed Securities | Farm & Ranch | Total Past Due
Guarantor Obligations [Line Items]
Total	8,238	14,966
LTSPCs and Farmer Mac Guaranteed Securities | Farm & Ranch | 30-59 Days
Guarantor Obligations [Line Items]
Total	6,026	2,189
LTSPCs and Farmer Mac Guaranteed Securities | Farm & Ranch | 60-89 Days
Guarantor Obligations [Line Items]
Total	45	1,344
LTSPCs and Farmer Mac Guaranteed Securities | Farm & Ranch | 90 Days and Greater
Guarantor Obligations [Line Items]
Total	2,167	11,433
LTSPCs | Rural Utilities
Guarantor Obligations [Line Items]
Total	574,255	556,425
LTSPCs | Rural Utilities | Current
Guarantor Obligations [Line Items]
Total	574,255	556,425
LTSPCs | Rural Utilities | Total Past Due
Guarantor Obligations [Line Items]
Total	0	0
LTSPCs | Rural Utilities | 30-59 Days
Guarantor Obligations [Line Items]
Total	0	0
LTSPCs | Rural Utilities | 60-89 Days
Guarantor Obligations [Line Items]
Total	0	0
LTSPCs | Rural Utilities | 90 Days and Greater
Guarantor Obligations [Line Items]
Total	$ 0	$ 0