Long-Term Debt - Summary of long-term debt outstanding and the weighted-average effective interest rates (Details) - USD ($) $ in Thousands	May 31, 2023	May 31, 2022
Debt Instrument [Line Items]
Total	$ 23,946,548	$ 21,545,440
Weighted- Average Interest Rate	3.44%	2.68%
Collateral trust bonds
Debt Instrument [Line Items]
Long-term debt, gross	$ 7,792,711	$ 7,097,711
Unamortized discount	(178,832)	(216,608)
Debt issuance costs	(35,906)	(32,613)
Total	$ 7,577,973	$ 6,848,490
Weighted- Average Interest Rate	3.46%	3.17%
Guaranteed Underwriter Program notes payable
Debt Instrument [Line Items]
Long-term debt, gross	$ 6,720,643	$ 6,105,473
Weighted- Average Interest Rate	3.09%	2.69%
Farmer Mac notes payable
Debt Instrument [Line Items]
Long-term debt, gross		$ 3,094,679
Total	$ 3,149,898
Weighted- Average Interest Rate	3.92%	2.33%
Other secured notes payable
Debt Instrument [Line Items]
Long-term debt, gross	$ 1,098	$ 2,755
Debt issuance costs	(2)	(9)
Total	$ 1,096	$ 2,746
Weighted- Average Interest Rate	3.06%	3.10%
Secured notes payable
Debt Instrument [Line Items]
Total	$ 9,871,637	$ 9,202,898
Secured long-term debt
Debt Instrument [Line Items]
Total	$ 17,449,610	$ 16,051,388
Weighted- Average Interest Rate	3.40%	2.83%
Medium-term notes sold through dealers
Debt Instrument [Line Items]
Long-term debt, gross	$ 6,152,726	$ 5,263,496
Weighted- Average Interest Rate	3.52%	2.20%
Medium-term notes to members
Debt Instrument [Line Items]
Long-term debt, gross	$ 365,260	$ 250,397
Weighted- Average Interest Rate	3.98%	2.70%
Unsecured medium-term notes
Debt Instrument [Line Items]
Long-term debt, gross	$ 6,517,986	$ 5,513,893
Unamortized premium (discount), net	4	(2,086)
Debt issuance costs	(21,122)	(19,723)
Total	$ 6,496,868	$ 5,492,084
Weighted- Average Interest Rate	3.55%	2.22%
Unsecured notes payable
Debt Instrument [Line Items]
Long-term debt, gross	$ 71	$ 1,979
Unamortized discount	(1)	(10)
Debt issuance costs	$ 0	$ (1)
Weighted- Average Interest Rate	0.00%	0.00%
Total unsecured notes payable
Debt Instrument [Line Items]
Total	$ 70	$ 1,968
Unsecured long-term debt
Debt Instrument [Line Items]
Total	$ 6,496,938	$ 5,494,052
Weighted- Average Interest Rate	3.55%	2.22%