Consolidated Statements of Changes in Equity (Deficit) - USD ($)	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Total Greystone Stockholders' Equity (Deficit) [Member]	Variable Interest Entities [Member]	Total
Balance at May. 31, 2015	$ 5	$ 2,741	$ 53,503,435	$ (55,657,638)	$ (2,151,457)	$ 1,016,127	$ (1,135,330)
Balance, shares at May. 31, 2015	50,000	27,411,201
Common stock options exercised		$ 48	56,952		57,000		$ 57,000
Common stock options exercised, shares		475,000					(475,000)
Stock based compensation			53,424		53,424		$ 53,424
Cash distributions						(204,000)	(204,000)
Preferred dividends				(331,575)	(331,575)		(331,575)
Net income				603,301	603,301	232,833	836,134
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)
Cash distributions						(213,609)	$ (213,609)
Preferred dividends				(345,822)	(345,822)		(345,822)
Issuance of warrants			120,000		120,000		120,000
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