Note 7 - Share Capital (Details Textual) $ / shares in Units, $ in Millions			6 Months Ended
	Feb. 04, 2015 USD ($)	Jan. 29, 2015 £ / shares shares	Jun. 30, 2015 £ / shares shares	Jan. 29, 2015 $ / shares shares	Dec. 31, 2014 £ / shares shares
Private Placement [Member]
Stock Issued During Period, Shares, New Issues		4,255,319
Shares Issued, Price Per Share | $ / shares				$ 11.75
Underwriters [Member]
Shares Issued, Price Per Share | $ / shares				$ 11.045
Common Stock, Shares, Outstanding			22,532,344		17,614,650
Common Stock, Par or Stated Value Per Share | £ / shares		£ 0.006705	£ 0.006705		£ 0.006705
Time Period for Underwriters to Exercise Share Grants from Date of Prospectus		30 days
Additional Shares Granted to Underwritten in Private Placement		638,297		638,297
Proceeds from Issuance of Private Placement, Gross | $	$ 57.5
Proceeds from Issuance of Private Placement | $	$ 53.8
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			24,078
Common Stock, Shares Authorized			36,183,293		36,183,293
Common Stock, Shares, Issued			22,532,344		17,614,650