CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Feb. 29, 2016	Feb. 28, 2015	Feb. 29, 2016	Feb. 28, 2015
Statement of Comprehensive Income [Abstract]
Net loss	$ (174,382)	$ (34,196)	$ (155,775)	$ (49,496)
Other comprehensive income (loss):
Unrealized gains (losses) on available-for-sale investment securities	(2,297)	1,644	589	5,246
Reclassification of derivative gains to net income	(218)	(239)	(689)	(722)
Defined benefit plan adjustments	43	(1,062)	131	(1,062)
Other comprehensive income (loss)	(2,472)	343	31	3,462
Total comprehensive loss	(176,854)	(33,853)	(155,744)	(46,034)
Less: Total comprehensive loss attributable to noncontrolling interests	1,402	220	1,985	221
Total comprehensive loss attributable to CFC	$ (175,452)	$ (33,633)	$ (153,759)	$ (45,813)