Note 7 - Stockholders' Equity (Details Textual) - USD ($)	3 Months Ended		29 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Nov. 30, 2016
Stock Repurchased During Period, Value	$ 23,000	$ 854,000
Class of Warrant or Right, Outstanding	10,088,074		10,088,074
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 11.50		$ 11.50
Common Stock [Member]
Stock Repurchased During Period, Shares	1,895	9,030
Stock Repurchased During Period, Value
Stock and Warrant Repurchase Plan [Member]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased				35,000,000
Warrants Repurchased During Period			6,011,926
Warrants Repurchased During Period, Value			$ 14,700,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 12,100,000		$ 12,100,000
Stock and Warrant Repurchase Plan [Member] | Common Stock [Member]
Warrants Repurchased During Period	1,895
Warrants Repurchased During Period, Value	$ 23,000
Stock Repurchased During Period, Shares			866,701
Stock Repurchased During Period, Value			$ 8,200,000