Loans - Schedule of Payment Status of Loans Outstanding (Details) - USD ($) $ in Thousands	Feb. 28, 2026	May 31, 2025	Feb. 28, 2025
Payment Status of Loans
Amount	$ 38,731,679	$ 37,063,548	$ 36,463,440
Nonaccrual Loans	$ 12,887	$ 26,099
Current, Percentage of total loans	100.00%	100.00%
30-89 days past due, Percentage of total loans	0.00%	0.00%
> 90 days past due, Percentage of total loans	0.00%	0.00%
Total past due, Percentage of total loans	0.00%	0.00%
Total loans outstanding, Percentage of total loans	100.00%	100.00%
Nonaccrual loans, Percentage of total loans	0.03%	0.07%
CFC:
Payment Status of Loans
Amount	$ 36,949,300	$ 35,409,320
Nonaccrual Loans	12,887	26,099
CFC: | Distribution
Payment Status of Loans
Amount	30,387,286	29,262,495
Nonaccrual Loans	0	0
CFC: | Power supply
Payment Status of Loans
Amount	6,288,837	5,895,500
Nonaccrual Loans	12,887	26,099
CFC: | Statewide and associate
Payment Status of Loans
Amount	273,177	251,325
Nonaccrual Loans	0	0
NCSC:
Payment Status of Loans
Amount	1,782,379	1,654,228
Nonaccrual Loans	0	0
NCSC: | Electric
Payment Status of Loans
Amount	1,163,391	1,078,763
Nonaccrual Loans	0	0
NCSC: | Telecom
Payment Status of Loans
Amount	618,988	575,465
Nonaccrual Loans	0	0
Current
Payment Status of Loans
Amount	38,731,679	37,063,548
Current | CFC:
Payment Status of Loans
Amount	36,949,300	35,409,320
Current | CFC: | Distribution
Payment Status of Loans
Amount	30,387,286	29,262,495
Current | CFC: | Power supply
Payment Status of Loans
Amount	6,288,837	5,895,500
Current | CFC: | Statewide and associate
Payment Status of Loans
Amount	273,177	251,325
Current | NCSC:
Payment Status of Loans
Amount	1,782,379	1,654,228
Current | NCSC: | Electric
Payment Status of Loans
Amount	1,163,391	1,078,763
Current | NCSC: | Telecom
Payment Status of Loans
Amount	618,988	575,465
Total Past Due
Payment Status of Loans
Amount	0	0
Total Past Due | CFC:
Payment Status of Loans
Amount	0	0
Total Past Due | CFC: | Distribution
Payment Status of Loans
Amount	0	0
Total Past Due | CFC: | Power supply
Payment Status of Loans
Amount	0	0
Total Past Due | CFC: | Statewide and associate
Payment Status of Loans
Amount	0	0
Total Past Due | NCSC:
Payment Status of Loans
Amount	0	0
Total Past Due | NCSC: | Electric
Payment Status of Loans
Amount	0	0
Total Past Due | NCSC: | Telecom
Payment Status of Loans
Amount	0	0
30-89 Days Past Due
Payment Status of Loans
Amount	0	0
30-89 Days Past Due | CFC:
Payment Status of Loans
Amount	0	0
30-89 Days Past Due | CFC: | Distribution
Payment Status of Loans
Amount	0	0
30-89 Days Past Due | CFC: | Power supply
Payment Status of Loans
Amount	0	0
30-89 Days Past Due | CFC: | Statewide and associate
Payment Status of Loans
Amount	0	0
30-89 Days Past Due | NCSC:
Payment Status of Loans
Amount	0	0
30-89 Days Past Due | NCSC: | Electric
Payment Status of Loans
Amount	0	0
30-89 Days Past Due | NCSC: | Telecom
Payment Status of Loans
Amount	0	0
> 90 Days Past Due
Payment Status of Loans
Amount	0	0
> 90 Days Past Due | CFC:
Payment Status of Loans
Amount	0	0
> 90 Days Past Due | CFC: | Distribution
Payment Status of Loans
Amount	0	0
> 90 Days Past Due | CFC: | Power supply
Payment Status of Loans
Amount	0	0
> 90 Days Past Due | CFC: | Statewide and associate
Payment Status of Loans
Amount	0	0
> 90 Days Past Due | NCSC:
Payment Status of Loans
Amount	0	0
> 90 Days Past Due | NCSC: | Electric
Payment Status of Loans
Amount	0	0
> 90 Days Past Due | NCSC: | Telecom
Payment Status of Loans
Amount	$ 0	$ 0