CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - USD ($)	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
February 11, 2014 Offering [Member]
Issuance costs			$ 1,458,000
December 27, 2012 Financing [Member]
Issuance costs			1,504,000
Series E Preferred Stock [Member]
Issuance costs	$ 1,000	$ 1,002,000	1,458,000
Series E Preferred Stock [Member] | February 11, 2014 Offering [Member]
Issuance costs			1,458,000
Series E Preferred Stock [Member] | June 13, 2014 Financing [Member]
Issuance costs	1,000	1,002,000
Common Stock
Issuance costs	677,000	513,000	$ 1,504,000
Common Stock | December 27, 2012 Financing [Member]
Issuance costs		161,000
Common Stock | June 13, 2014 Financing [Member]
Issuance costs	311,000	$ 352,000
Common Stock | August 7, 2015 Financing [Member]
Issuance costs	365,000
Common Stock | October 30, 2015 Financing [Member]
Issuance costs	$ 1,000