CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	May 31, 2018	May 31, 2017	May 31, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 457,364	$ 312,099	$ (51,516)
Other comprehensive income (loss):
Unrealized gains (losses) on available-for-sale investment securities	(3,222)	4,614	3,468
Unrealized losses on foreclosed assets	0	0	(5,575)
Unrealized losses on cash flow hedges	(1,059)	0	0
Reclassification of losses on foreclosed assets to net income	0	9,823	0
Reclassification of derivative gains to net income	(663)	(785)	(888)
Defined benefit plan adjustments	313	(1,535)	(31)
Other comprehensive income (loss)	(4,631)	12,117	(3,026)
Total comprehensive income (loss)	452,733	324,216	(54,542)
Less: Total comprehensive (income) loss attributable to noncontrolling interests	(2,178)	(2,193)	1,867
Total comprehensive income (loss) attributable to CFC	$ 450,555	$ 322,023	$ (52,675)