Note 9 - Stockholders' Equity - Options Outstanding and Vested (Details)	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Options Outstanding (in shares) | shares	7,401
Weighted Average Remaining Contractual Life (Year)	6 years 295 days
Weighted Average Exercise Price (in dollars per share)	$ 1,309.47
Number Exercisable (in shares) | shares	7,224
Weighted Average Exercise Price, options vested (in dollars per share)	$ 1,310.25
Exercise Price Range 1 [Member]
Exercise Price (in dollars per share)	$ 16.70
Options Outstanding (in shares) | shares	3,100
Weighted Average Remaining Contractual Life (Year)	8 years 160 days
Weighted Average Exercise Price (in dollars per share)	$ 16.70
Number Exercisable (in shares) | shares	3,100
Weighted Average Exercise Price, options vested (in dollars per share)	$ 16.70
Exercise Price Range 2 [Member]
Exercise Price (in dollars per share)	$ 204
Options Outstanding (in shares) | shares	5
Weighted Average Remaining Contractual Life (Year)	7 years 204 days
Weighted Average Exercise Price (in dollars per share)	$ 204
Number Exercisable (in shares) | shares	3
Weighted Average Exercise Price, options vested (in dollars per share)	$ 204
Exercise Price Range 3 [Member]
Exercise Price (in dollars per share)	$ 820
Options Outstanding (in shares) | shares	1,001
Weighted Average Remaining Contractual Life (Year)	7 years 76 days
Weighted Average Exercise Price (in dollars per share)	$ 820
Number Exercisable (in shares) | shares	856
Weighted Average Exercise Price, options vested (in dollars per share)	$ 820
Exercise Price Range 4 [Member]
Exercise Price (in dollars per share)	$ 1,052
Options Outstanding (in shares) | shares	46
Weighted Average Remaining Contractual Life (Year)	7 years 65 days
Weighted Average Exercise Price (in dollars per share)	$ 1,052
Number Exercisable (in shares) | shares	36
Weighted Average Exercise Price, options vested (in dollars per share)	$ 1,052
Exercise Price Range 5 [Member]
Exercise Price (in dollars per share)	$ 1,420
Options Outstanding (in shares) | shares	70
Weighted Average Remaining Contractual Life (Year)	6 years 306 days
Weighted Average Exercise Price (in dollars per share)	$ 1,420
Number Exercisable (in shares) | shares	70
Weighted Average Exercise Price, options vested (in dollars per share)	$ 1,420
Exercise Price Range 6 [Member]
Exercise Price (in dollars per share)	$ 1,472
Options Outstanding (in shares) | shares	10
Weighted Average Remaining Contractual Life (Year)	6 years 302 days
Weighted Average Exercise Price (in dollars per share)	$ 1,472
Number Exercisable (in shares) | shares	8
Weighted Average Exercise Price, options vested (in dollars per share)	$ 1,472
Exercise Price Range 7 [Member]
Exercise Price (in dollars per share)	$ 1,800
Options Outstanding (in shares) | shares	2,440
Weighted Average Remaining Contractual Life (Year)	5 years
Weighted Average Exercise Price (in dollars per share)	$ 1,800
Number Exercisable (in shares) | shares	2,440
Weighted Average Exercise Price, options vested (in dollars per share)	$ 1,800
Exercise Price Range 8 [Member]
Exercise Price (in dollars per share)	$ 1,980
Options Outstanding (in shares) | shares	28
Weighted Average Remaining Contractual Life (Year)	116 days
Weighted Average Exercise Price (in dollars per share)	$ 1,980
Number Exercisable (in shares) | shares	28
Weighted Average Exercise Price, options vested (in dollars per share)	$ 1,980
Exercise Price Range 9 [Member]
Exercise Price (in dollars per share)	$ 4,364
Options Outstanding (in shares) | shares	10
Weighted Average Remaining Contractual Life (Year)	5 years 65 days
Weighted Average Exercise Price (in dollars per share)	$ 1,980
Number Exercisable (in shares) | shares	10
Weighted Average Exercise Price, options vested (in dollars per share)	$ 1,980
Exercise Price Range 10 [Member]
Exercise Price (in dollars per share)	$ 4,404
Options Outstanding (in shares) | shares	25
Weighted Average Remaining Contractual Life (Year)	6 years 156 days
Weighted Average Exercise Price (in dollars per share)	$ 4,404
Number Exercisable (in shares) | shares	25
Weighted Average Exercise Price, options vested (in dollars per share)	$ 4,404
Exercise Price Range 11 [Member]
Exercise Price (in dollars per share)	$ 4,952
Options Outstanding (in shares) | shares	18
Weighted Average Remaining Contractual Life (Year)	6 years 120 days
Weighted Average Exercise Price (in dollars per share)	$ 4,952
Number Exercisable (in shares) | shares	18
Weighted Average Exercise Price, options vested (in dollars per share)	$ 4,952
Exercise Price Range 12 [Member]
Exercise Price (in dollars per share)	$ 5,040
Options Outstanding (in shares) | shares	24
Weighted Average Remaining Contractual Life (Year)	1 year 171 days
Weighted Average Exercise Price (in dollars per share)	$ 5,040
Number Exercisable (in shares) | shares	24
Weighted Average Exercise Price, options vested (in dollars per share)	$ 5,040
Exercise Price Range 13 [Member]
Exercise Price (in dollars per share)	$ 5,184
Options Outstanding (in shares) | shares	151
Weighted Average Remaining Contractual Life (Year)	6 years 69 days
Weighted Average Exercise Price (in dollars per share)	$ 5,184
Number Exercisable (in shares) | shares	141
Weighted Average Exercise Price, options vested (in dollars per share)	$ 5,184
Exercise Price Range 14 [Member]
Exercise Price (in dollars per share)	$ 5,196
Options Outstanding (in shares) | shares	241
Weighted Average Remaining Contractual Life (Year)	6 years 65 days
Weighted Average Exercise Price (in dollars per share)	$ 5,196
Number Exercisable (in shares) | shares	233
Weighted Average Exercise Price, options vested (in dollars per share)	$ 5,196
Exercise Price Range 15 [Member]
Exercise Price (in dollars per share)	$ 5,940
Options Outstanding (in shares) | shares	14
Weighted Average Remaining Contractual Life (Year)	2 years 7 days
Weighted Average Exercise Price (in dollars per share)	$ 5,940
Number Exercisable (in shares) | shares	14
Weighted Average Exercise Price, options vested (in dollars per share)	$ 5,940
Exercise Price Range 16 [Member]
Exercise Price (in dollars per share)	$ 6,084
Options Outstanding (in shares) | shares	11
Weighted Average Remaining Contractual Life (Year)	5 years 211 days
Weighted Average Exercise Price (in dollars per share)	$ 6,084
Number Exercisable (in shares) | shares	11
Weighted Average Exercise Price, options vested (in dollars per share)	$ 6,084
Exercise Price Range 17 [Member]
Exercise Price (in dollars per share)	$ 7,290
Options Outstanding (in shares) | shares	3
Weighted Average Remaining Contractual Life (Year)	4 years 14 days
Weighted Average Exercise Price (in dollars per share)	$ 7,290
Number Exercisable (in shares) | shares	3
Weighted Average Exercise Price, options vested (in dollars per share)	$ 7,290
Exercise Price Range 18 [Member]
Exercise Price (in dollars per share)	$ 7,844
Options Outstanding (in shares) | shares	110
Weighted Average Remaining Contractual Life (Year)	5 years 332 days
Weighted Average Exercise Price (in dollars per share)	$ 7,844
Number Exercisable (in shares) | shares	110
Weighted Average Exercise Price, options vested (in dollars per share)	$ 7,844
Exercise Price Range 19 [Member]
Exercise Price (in dollars per share)	$ 8,100
Options Outstanding (in shares) | shares	94
Weighted Average Remaining Contractual Life (Year)	3 years 266 days
Weighted Average Exercise Price (in dollars per share)	$ 8,100
Number Exercisable (in shares) | shares	94
Weighted Average Exercise Price, options vested (in dollars per share)	$ 8,100