Note 7 - Stockholders' Equity (Details) - Exercise Price Ranges (USD $)	12 Months Ended
Dec. 31, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding (in Shares)	7,918,004
Price Range 1 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding (in Shares)	953,090
Lower exercise price	$ 3.80
Exercise price	$ 5.34
Upper exercise price	$ 7.00
Weighted-average remaining contractual life, outstanding	5 years 335 days
Weighted-average exercise price	$ 5.78
Options exercisable (in Shares)	662,840
Weighted-average exercise price of options exercisable	$ 5.34
Price Range 2 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding (in Shares)	2,511,808
Exercise price	$ 7.20
Weighted-average remaining contractual life, outstanding	8 years 3 days
Weighted-average exercise price	$ 7.20
Options exercisable (in Shares)	531,578
Weighted-average exercise price of options exercisable	$ 7.20
Price Range 3 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding (in Shares)	2,428,458
Lower exercise price	$ 7.61
Exercise price	$ 8.95
Upper exercise price	$ 9.05
Weighted-average remaining contractual life, outstanding	9 years 43 days
Weighted-average exercise price	$ 8.87
Options exercisable (in Shares)	204,669
Weighted-average exercise price of options exercisable	$ 8.95
Price Range 4 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding (in Shares)	1,991,338
Lower exercise price	$ 9.20
Exercise price	$ 12.09
Upper exercise price	$ 15.40
Weighted-average remaining contractual life, outstanding	7 years 153 days
Weighted-average exercise price	$ 11.27
Options exercisable (in Shares)	805,504
Weighted-average exercise price of options exercisable	$ 12.09
Price Range 5 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding (in Shares)	33,310
Lower exercise price	$ 15.41
Exercise price	$ 36.97
Upper exercise price	$ 139.20
Weighted-average remaining contractual life, outstanding	1 year 18 days
Weighted-average exercise price	$ 36.97
Options exercisable (in Shares)	33,310
Weighted-average exercise price of options exercisable	$ 36.97
Price Range 6 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding (in Shares)	7,918,004
Lower exercise price	$ 3.80
Exercise price	$ 9.01
Upper exercise price	$ 139.20
Weighted-average remaining contractual life, outstanding	7 years 335 days
Weighted-average exercise price	$ 8.69
Options exercisable (in Shares)	2,237,901
Weighted-average exercise price of options exercisable	$ 9.01

Weighted average exercise price as of the balance sheet date for those equity-based payment arrangements exercisable and outstanding.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

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The number of shares reserved for issuance pertaining to the outstanding exercisable stock options as of the balance sheet date in the customized range of exercise prices for which the market and performance vesting condition has been satisfied.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

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The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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Weighted average remaining contractual term of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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