Note 12 - Income Taxes - Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income tax rate	20.00%	20.30%	21.50%
Effective income tax rate	17.00%
Her Majesty's Revenue and Customs (HMRC) [Member]
Income tax rate	20.00%	20.30%	21.50%
U.K. research and development credit	1.80%	1.30%	1.70%
Other	(2.10%)	(1.10%)	(1.20%)
Effect of foreign tax rate differential	16.80%	10.70%	17.90%
Valuation allowance	(22.10%)	(31.70%)	(40.60%)
Effective income tax rate	14.40%	(0.50%)	(0.70%)