Note 2 - Stock-based Compensation - Stock Incentive Plan Activities (Details) - Incentive Plan [Member] shares in Thousands	9 Months Ended
Sep. 30, 2018 $ / shares shares
Awards available, beginning balance (in shares)	468
Options outstanding, beginning balance (in shares)	14,452
Weighted average exercise price, beginning balance (in dollars per share) \| $ / shares	$ 6.06
Awards available, restricted stock awards granted (in shares)	(10)
Awards available, restricted stock awards cancelled (in shares)
Awards available, stock option awards granted (in shares)	(321)
Options outstanding, stock option awards granted (in shares)	321
Weighted average exercise price, stock option awards granted (in dollars per share) \| $ / shares	$ 6.12
Options outstanding, stock option awards exercised (in shares)	(572)
Weighted average exercise price, stock option awards exercised (in dollars per share) \| $ / shares	$ 2.78
Awards available, stock option awards cancelled (in shares)	143
Options outstanding, stock option awards cancelled (in shares)	(143)
Weighted average exercise price, stock option awards cancelled (in dollars per share) \| $ / shares	$ 6.08
Awards available, ending balance (in shares)	280
Options outstanding, ending balance (in shares)	14,058
Weighted average exercise price, ending balance (in dollars per share) \| $ / shares	$ 6.20

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No definition available.

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- Definition

Share based compensation arrangement by share based payment award options forfeitures in period awards available.

+ References

No definition available.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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- Definition

For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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- Definition

Net number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

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- Definition

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

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Number of share options (or share units) exercised during the current period.

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