CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	May 31, 2021	May 31, 2020	May 31, 2019
Income Statement [Abstract]
Interest income	$ 1,116,601	$ 1,151,286	$ 1,135,670
Interest expense	(702,063)	(821,089)	(836,209)
Net interest income	414,538	330,197	299,461
Benefit (provision) for credit losses	(28,507)	(35,590)	1,266
Net interest income after benefit (provision) for credit losses	386,031	294,607	300,727
Non-interest income:
Fee and other income	18,929	22,961	15,355
Derivative gains (losses)	506,301	(790,151)	(363,341)
Investment securities gains (losses)	1,495	9,431	(1,799)
Total non-interest income	526,725	(757,759)	(349,785)
Non-interest expense:
Salaries and employee benefits	(55,258)	(54,522)	(49,824)
Other general and administrative expenses	(39,447)	(46,645)	(43,342)
Losses on early extinguishment of debt	(1,456)	(683)	(7,100)
Other non-interest expense	(1,619)	(25,588)	(1,675)
Total non-interest expense	(97,780)	(127,438)	(101,941)
Income (loss) before income taxes	814,976	(590,590)	(150,999)
Income tax benefit (provision)	(998)	1,160	(211)
Net income (loss)	813,978	(589,430)	(151,210)
Less: Net (income) loss attributable to noncontrolling interests	(2,311)	4,190	1,979
Net income (loss) attributable to CFC	$ 811,667	$ (585,240)	$ (149,231)