Equity - Schedule of components of equity (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2026	May 31, 2025	May 31, 2024	May 31, 2023
Membership fees and educational fund:
Prior fiscal year-end cumulative derivative forward value gains	$ 501,663	$ 606,215
Current fiscal year derivative forward value gains (losses)	(18,213)	105,070	$ (264,871)
Current fiscal year-end cumulative derivative forward value gains	519,419	501,663
CFC retained equity	3,292,893	3,084,713
Accumulated other comprehensive loss	(2,369)	(2,236)
Total CFC equity	3,290,524	3,082,477
Noncontrolling interests	21,612	20,989
Total equity	3,312,136	3,103,466	3,012,169	$ 2,589,249
Total membership fees and educational fund
Membership fees and educational fund:
Total members' equity	3,769	3,624
Total equity	3,769	3,624	3,576	3,534
Membership fees
Membership fees and educational fund:
Total members' equity	969	966
Educational fund
Membership fees and educational fund:
Total members' equity	2,800	2,658
Patronage Capital Allocated
Membership fees and educational fund:
Total members' equity	966,253	948,526
Total equity	966,253	948,526	928,232	1,006,115
Members’ capital reserve
Membership fees and educational fund:
Total members' equity	1,804,161	1,631,609
Total equity	1,804,161	1,631,609	1,455,564	1,202,152
Other unallocated net loss
Membership fees and educational fund:
Total members' equity	(709)	(709)
Unallocated net income
Membership fees and educational fund:
Total equity	518,710	500,954	$ 605,506	$ 341,915
CFC
Membership fees and educational fund:
Current fiscal year derivative forward value gains (losses)	$ 17,756	$ (104,552)