Loans - Additional Information - Credit Concentration (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Feb. 28, 2026 USD ($) borrower member power_supply_system loan distribution_system	May 31, 2025 USD ($) power_supply_system borrower distribution_system member	Feb. 28, 2025 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans to members	$ 38,749,882	$ 37,079,978	$ 36,479,209
Number of active borrowers | borrower	908	899
Number of states with active borrowers | member	49	49
Loans | Geographic Concentration Risk | TEXAS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans to members	$ 6,258,000	$ 6,105,000
Concentration risk, percentage	16.00%	16.00%
Number of active borrowers | borrower	67	68
Power supply
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of active borrowers | borrower	49	50
Loans Receivable Commercial And Industrial | Loans | Customer Concentration Risk | Twenty Largest Borrowers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans to members	$ 7,248,000	$ 7,149,000
Concentration risk, percentage	19.00%	19.00%
Concentration risk, number of borrowers | borrower	20	20
Loans Receivable Commercial And Industrial | Loans | Customer Concentration Risk | Largest Single Borrower Or Controlled Group
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percentage	1.00%	1.00%
Loans Receivable Commercial And Industrial | Electric | Loans | Credit Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans to members	$ 38,113,000	$ 36,488,000
Loans Receivable Commercial And Industrial | Distribution | Loans | Customer Concentration Risk | Twenty Largest Borrowers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, number of borrowers | distribution_system	13	14
Loans Receivable Commercial And Industrial | Power supply | Loans | Customer Concentration Risk | Twenty Largest Borrowers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, number of borrowers | power_supply_system	7	6
Loans and Finance Receivables | Loans | Credit Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percentage	98.00%	98.00%
Loans Guaranteed By Rural Utilities Service
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans to members	$ 97,000	$ 105,000
Loans Guaranteed By Farmer Mac
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans to members	$ 327,000	346,000
Number of loans that defaulted | loan	0
Number of defaulted loans put to Farmer Mac for purchase | loan	0
Loans Guaranteed By Farmer Mac | Loans | Credit Concentration Risk | Twenty Largest Borrowers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans to members	$ 205,000	$ 155,000
Concentration risk, number of borrowers | borrower	20	20
Loans Guaranteed By Farmer Mac | Loans | Customer Concentration Risk | Twenty Largest Borrowers
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans to members	$ 7,043,000	$ 6,994,000
Concentration risk, number of borrowers | borrower	20	20
Loans Guaranteed By Farmer Mac | Loans | Geographic Concentration Risk | TEXAS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans to members	$ 111,000	$ 118,000
Loans receivable commercial and industrial not covered by Farmer Mac standby repurchase agreement | Loans | Geographic Concentration Risk | TEXAS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans to members	$ 6,147,000	$ 5,987,000