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Note 8 - Acquisition of EGEN, Inc. (Details Textual) - USD ($)				1 Months Ended	3 Months Ended		12 Months Ended
	Aug. 02, 2016	Jun. 20, 2014	Jun. 10, 2014	Jun. 20, 2014	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Jun. 09, 2014
EGEN Inc [Member] \| Maximum [Member]
Business Combination, Consideration Transferred		$ 44,400,000
EGEN Inc [Member] \| Scenario, Forecast [Member]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares	670,070
EGEN Inc [Member] \| Ovarian Cancer Study Milestone [Member]
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	$ 12,400,000
EGEN Inc [Member] \| Glioblastoma Multiforme Brain Cancer Study Milestone [Member]
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	12,000,000
EGEN Inc [Member] \| TheraSilence Technology Milestone [Member]
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	$ 6,000,000
EGEN Inc [Member] \| Hercules Credit Agreement [Member]
Payments to Acquire Businesses, Gross			$ 3,000,000
Loans Payable									$ 5,000,000
EGEN Inc [Member] \| In Process Research and Development [Member]
Finite-lived Intangible Assets Acquired		25,800,000
EGEN Inc [Member]
Business Combination, Consideration Transferred		27,600,000		$ 27,578,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High		30,400,000		$ 30,400,000	$ 30,400,000
Payments to Acquire Businesses, Gross		$ 3,000,000
Stock Issued During Period, Shares, Acquisitions		2,712,188		2,712,188	2,712,188
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares				670,070	670,070
Business Combination, Consideration Transferred, Liabilities Incurred		$ 13,900,000		$ 13,878,000	$ 14,200,000	$ 13,800,000	$ 13,900,000	$ 13,700,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability					302,656	172,136
Goodwill, Acquired During Period		$ 2,000,000
Business Combination, Consideration Transferred, Liabilities Incurred					$ 302,656	$ 13,800,000		$ 13,700,000