Note 8 - Stockholders' Equity (Deficiency) - Outstanding Options Granted to Consultants for Sales and Pre-marketing Services (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Granted (in dollars per share)	$ 16.87	$ 28.253	$ 25.077
Options exercisable at the end of the year (in shares)	1,752,416	1,794,249	2,620,454
Exercise price per share (in dollars per share)	$ 16.87	$ 28.253	$ 25.077
Consultants [Member]
Options for shares of common stock (in shares)	44,384	49,430
Options exercisable at the end of the year (in shares)	23,000	18,991
February 2013 [Member] | Consultants [Member]
Options for shares of common stock (in shares)	1,500	3,000
Granted (in dollars per share)	$ 12.47	$ 12.47
Options exercisable at the end of the year (in shares)	1,344	2,125
Exercisable through	February 2023	February 2023
Exercise price per share (in dollars per share)	$ 12.47	$ 12.47
August 2013 [Member] | Consultants [Member]
Options for shares of common stock (in shares)	4,188	5,000
Granted (in dollars per share)	$ 21.14	$ 21.14
Options exercisable at the end of the year (in shares)	3,104	2,917
Exercisable through	August 2023	August 2023
Exercise price per share (in dollars per share)	$ 21.14	$ 21.14
October 2013 [Member] | Consultants [Member]
Options for shares of common stock (in shares)	750	823
Granted (in dollars per share)	$ 24.23	$ 24.23
Options exercisable at the end of the year (in shares)	547	479
Exercisable through	October 2023	October 2023
Exercise price per share (in dollars per share)	$ 24.23	$ 24.23
March 2014 [Member] | Consultants [Member]
Options for shares of common stock (in shares)	13,100	14,438
Granted (in dollars per share)	$ 39.86	$ 39.86
Options exercisable at the end of the year (in shares)	8,187	6,422
Exercisable through	March 2024	March 2024
Exercise price per share (in dollars per share)	$ 39.86	$ 39.86
May 2014 [Member] | Consultants [Member]
Options for shares of common stock (in shares)	6,850	8,700
Granted (in dollars per share)	$ 22.01	$ 22.01
Options exercisable at the end of the year (in shares)	3,704	3,444
Exercisable through	May 2024	May 2024
Exercise price per share (in dollars per share)	$ 22.01	$ 22.01
November 2014 [Member] | Consultants [Member]
Options for shares of common stock (in shares)	10,246	12,000
Granted (in dollars per share)	$ 21.66	$ 21.66
Options exercisable at the end of the year (in shares)	4,364	3,250
Exercisable through	November 2024	November 2024
Exercise price per share (in dollars per share)	$ 21.66	$ 21.66
August 2014 [Member] | Consultants [Member]
Options for shares of common stock (in shares)		219
Granted (in dollars per share)		$ 21
Options exercisable at the end of the year (in shares)		354
Exercisable through		August 2024
Exercise price per share (in dollars per share)		$ 21
May 2015 [Member] | Consultants [Member]
Options for shares of common stock (in shares)	5,250	5,250
Granted (in dollars per share)	$ 19.51	$ 19.51
Options exercisable at the end of the year (in shares)	1,750
Exercisable through	May 2025	May 2025
Exercise price per share (in dollars per share)	$ 19.51	$ 19.51
February 2016 [Member] | Consultants [Member]
Options for shares of common stock (in shares)	2,500
Granted (in dollars per share)	$ 16.87
Options exercisable at the end of the year (in shares)
Exercisable through	February 2026
Exercise price per share (in dollars per share)	$ 16.87