Consolidated Statements of Changes in Equity - USD ($)	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Total Greystone Stockholders' Equity (Deficit) [Member]	Non-controlling Interest [Member]	Total
Balance at May. 31, 2016	$ 5	$ 2,789	$ 53,613,811	$ (55,385,912)	$ (1,769,307)	$ 1,044,960	$ (724,347)
Balance, shares at May. 31, 2016	50,000	27,886,201
Common stock options exercised		$ 47	56,953		57,000		$ 57,000
Common stock options exercised, shares		475,000					475,000
Issuance of warrants			120,000		120,000		$ 120,000
Cash distributions						(213,609)	(213,609)
Preferred dividends				(345,822)	(345,822)		(345,822)
Net income				2,006,743	2,006,743	240,165	2,246,908
Balance at May. 31, 2017	$ 5	$ 2,836	53,790,764	(53,724,991)	68,614	1,071,516	$ 1,140,130
Balance, shares at May. 31, 2017	50,000	28,361,201
Common stock options exercised, shares
Cash distributions						(233,400)	$ (233,400)
Preferred dividends				(384,384)	(384,384)		(384,384)
Net income				1,624,062	1,624,062	247,039	1,871,101
Balance at May. 31, 2018	$ 5	$ 2,836	$ 53,790,764	$ (52,485,313)	$ 1,308,292	$ 1,085,155	$ 2,393,447
Balance, shares at May. 31, 2018	50,000	28,361,201