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Weighted average purchase price of capital shares purchased through an employee stock ownership plan.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Note 7 - Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	1 Months Ended			12 Months Ended
	Dec. 31, 2019	Dec. 31, 2014	Aug. 31, 2013	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Payment Arrangement, Expense				$ 17,719	$ 9,396	$ 12,621
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross				5,891
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares				2,794
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value				$ 2.58
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total	$ 26,552			$ 26,552
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Expected to be Recognized Next Year	9,746			9,746
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Expected to be Recognized Year Two	7,950			7,950
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Expected to be Recognized Year Three	6,743			6,743
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Expected to be Recognized Year Four	$ 2,113			2,113
Incentive Plan [Member]
Share-based Payment Arrangement, Expense				$ 17,164	$ 9,223	$ 12,421
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value				$ 2.63	$ 4.92	$ 3.63
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price				$ 3.91	$ 7.15	$ 5.33
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance	21,050			21,050	17,491	14,452	12,095
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value				$ 1,127	$ 4,504	$ 1,964
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	968			968	805	468	2,273
Incentive Plan [Member] \| Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate				0.00%
Incentive Plan [Member] \| Share-based Payment Arrangement, Option [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term				10 years
Incentive Plan [Member] \| Share-based Payment Arrangement, Option [Member] \| Vest 25% Each Year Until Fully Vested [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage				25.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period				4 years
Incentive Plan [Member] \| Performance Shares [Member] \| December 2014 [Member]
Share-based Payment Arrangement, Expense				$ 4,998
Incentive Plan [Member] \| Performance Shares [Member] \| December 2019 [Member]
Share-based Payment Arrangement, Expense				$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares				0
Incentive Plan [Member] \| Performance Shares [Member] \| Vest Upon Successful Completion of Specific Development Milestones [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	315	1,250	1,032
Incentive Plan [Member] \| Performance Shares [Member] \| Vest Upon Successful Completion of Specific Development Milestones [Member] \| August 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage					75.00%
Incentive Plan [Member] \| Performance Shares [Member] \| Vest Upon Successful Completion of Specific Development Milestones [Member] \| December 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage					30.00%
Inducement Plan [Member]
Share-based Payment Arrangement, Expense				$ 323
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period				4 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross				1,379
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value				$ 2.41
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period				10 years
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price				$ 3.58
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance	1,329			1,329
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value				$ 0
Inducement Plan [Member] \| Vest 25% Each Year Until Fully Vested [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage				25.00%
Inducement Plan [Member] \| Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate				0.00%
Employee Stock Purchase Plan [Member]
Share-based Payment Arrangement, Expense				$ 232	$ 173	$ 200
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	1,475			1,475
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	119			119
Percentage of Salary to Purchase Common Stock, Maximum				15.00%
Percentage of Common Stock Shares, Beginning				85.00%
Percentage of Common Stock Shares, Ending				85.00%
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares Per Employee				3
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares Per Employee, Amount	$ 25			$ 25
Stock Issued During Period, Shares, Employee Stock Purchase Plans				115	92	95
Employee Stock Ownership Plan (ESOP), Weighted Average Purchase Price of Shares Purchased				$ 3.51	$ 3.83	$ 3.61
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value				$ 2.01	$ 1.89	$ 2.18
Incentive Plan and Inducement Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term				4 years 328 days
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate				0.00%	0.00%	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 3,926			$ 3,926
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value				$ 12,499	$ 8,952	$ 9,310
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	20,324			20,324
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 5.83			$ 5.83
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term				6 years 328 days