Note 5 - Fair Value Measurements - Fair Value of Financial Instruments (Details) - USD ($)	Jun. 30, 2015	Dec. 31, 2014
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Cash & cash equivalents:
Cash & cash equivalents	$ 60,814,116	$ 69,551,754
Money Market Funds [Member]
Cash & cash equivalents:
Cash & cash equivalents	60,814,116	69,551,754
Certificates of Deposit [Member] | Fair Value, Inputs, Level 2 [Member]
Cash & cash equivalents:
Cash & cash equivalents		3,000,000
Investments:
Investments	15,500,000	6,750,000
Certificates of Deposit [Member]
Cash & cash equivalents:
Cash & cash equivalents		3,000,000
Investments:
Investments	15,500,000	6,750,000
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Investments:
Investments	3,013,150
Corporate Debt Securities [Member]
Investments:
Investments	3,013,150
Fair Value, Inputs, Level 2 [Member]
Cash & cash equivalents:
Cash & cash equivalents		72,551,754
Investments:
Investments	18,513,150
Cash & cash equivalents		72,551,754
Investments	$ 18,513,150	$ 6,750,000