Equity - Narrative (Details) $ in Thousands	1 Months Ended			12 Months Ended
	Jul. 31, 2023 USD ($)	Jul. 31, 2022 USD ($)	May 31, 2022 USD ($)	May 31, 2023 USD ($) reserve	May 31, 2022 USD ($)	May 31, 2021 USD ($)	May 31, 2020 USD ($)
Equity
Stockholders' equity, period increase (decrease)				$ 447,000
Total equity			$ 2,141,969	2,589,249	$ 2,141,969	$ 1,399,879	$ 648,822
Net income				501,587	798,537	813,978
Patronage capital retirement				$ 61,840	59,979	61,911
Minimum percentage of paid-in-capital required to be maintained under District of Columbia cooperative law				50.00%
Cash flow hedging
Equity
Accumulated other comprehensive income expected to be reclassified into earnings over the next 12 months				$ 1,000
Patronage Capital Allocated
Equity
Total equity			954,988	1,006,115	954,988	923,970	894,066
Net income				110,273	88,583	89,761
Patronage capital retirement				59,136	57,565	59,857
Members’ Capital Reserve
Equity
Total equity			1,062,286	1,202,152	1,062,286	909,749	807,320
Net income				139,856	152,537	102,429
Membership Fees and Educational Fund
Equity
Total equity			3,387	3,534	3,387	3,125	$ 3,193
Net income				$ 1,100	$ 1,200	$ 900
CFC
Equity
General reserve required to be maintained as a percentage of membership fees collected				50.00%
Number of additional board-approved reserves | reserve				1
CFC | Cooperative educational fund | Minimum
Equity
Minimum percentage of net earnings to be allocated to cooperative education fund as per bylaws of the entity				0.25%
CFC | Patronage Capital Allocated
Equity
Net income		$ 89,000
Percentage of prior year's allocated patronage capital required to be retired				50.00%
Percentage of prior year's allocated patronage capital required to be held				50.00%
Period for which prior year's allocated patronage capital is required to be held				25 years
Retirement of allocated net earnings, percentage		50.00%
CFC | Patronage Capital Allocated | Subsequent event
Equity
Net income	$ 110,000
CFC | Retained Earnings, Appropriated Patronage Capital Allocated and Retired
Equity
Net income		$ 59,000
CFC | Retained Earnings, Appropriated Patronage Capital Allocated and Retired | Subsequent event
Equity
Net income	72,000
CFC | Retained earnings allocation of fifty percent of prior year patronage capital allocation
Equity
Net income		44,000
CFC | Retained earnings allocation of fifty percent of prior year patronage capital allocation | Subsequent event
Equity
Net income	$ 55,000
Retirement of allocated net earnings, percentage	50.00%
CFC | Retained earnings prior year allocation held for 25 years
Equity
Net income		$ 15,000
Period for which prior year's allocated patronage capital is required to be held		25 years
CFC | Retained earnings prior year allocation held for 25 years | Subsequent event
Equity
Net income	$ 17,000
Period for which prior year's allocated patronage capital is required to be held	25 years
CFC | Members’ Capital Reserve
Equity
Net income		$ 153,000
CFC | Members’ Capital Reserve | Subsequent event
Equity
Net income	$ 140,000
CFC | Membership Fees and Educational Fund
Equity
Net income			$ 1,000	$ 1,000
RTFC
Equity
Minimum percentage of paid-in-capital required to be maintained under District of Columbia cooperative law				50.00%
RTFC | Minimum
Equity
Percentage of retirement of allocated net earnings in cash				20.00%
RTFC | Cooperative educational fund | Minimum
Equity
Minimum percentage of net earnings to be allocated to cooperative education fund as per bylaws of the entity				1.00%
NCSC
Equity
Minimum percentage of paid-in-capital required to be maintained under District of Columbia cooperative law				50.00%
NCSC | Cooperative educational fund | Minimum
Equity
Minimum percentage of net earnings to be allocated to cooperative education fund as per bylaws of the entity				0.25%
RTFC
Equity
Percentage of ownership by minority owners				100.00%
NCSC
Equity
Percentage of ownership by parent				100.00%