Note 9 - Warrants	12 Months Ended
Dec. 31, 2017
Notes to Financial Statements
Warrants Disclosure [Text Block]	9. Warrants Amended and Restated Loan Agreement Warrants In connection with the Original Loan Agreement, executed in December 2013, the Company issued warrants to the Lenders which were exercisable for an aggregate of 176,730 shares of common stock with an exercise price of $6.79 per share, or the Warrants. In connection with Amendment No. 2 to the Original Loan Agreement, the Company reduced the exercise price of the warrants already held by the Lenders from the previous exercise price of $6.79 per share to $3.88 per share, or the First Warrant Amendments. In connection with Amendment No. 3 to the Original Loan Agreement, the Company reduced the exercise price of the warrants already held by the Lenders from the previous exercise price of $3.88 per share to $3.07 per share, or the Second Warrant Amendments. Each Warrant may be exercised on a cashless basis. The Warrants are exercisable for a term beginning on the date of issuance and ending on the earlier to occur of five years from the date of issuance or the consummation of certain acquisitions of the Company as set forth in the Warrants. The number of shares for which the Warrants are exercisable and the associated exercise price are subject to certain proportional adjustments as set forth in the Warrants. The Company estimated the fair value of these Warrants as of the issuance date to be $1.1 million, which was used in the estimating of the fair value of the amended debt instrument and was recorded as equity. The fair value of the Warrants was calculated using the Black-Scholes option-valuation model, and was based on the original strike price of $6.79, the stock price at issuance of $9.67, the five -year contractual term of the warrants, a risk-free interest rate of 1.55%, expected volatility of 71% and 0% expected dividend yield. The Company estimated the fair value of the modification of the First Warrant Amendments, as of the issuance date to be $0.1 million, which was used in estimating the fair value of the amended debt instrument in September 2015 and was recorded as equity, as well as the Second Warrant Amendments, which fair value was estimated to be $45.0 thousand at the issuance date, and which was used in estimating the fair value of the amended debt instrument in September 2016 and was recorded as equity. As of December 31, 2017, warrants to purchase 176,730 shares of common stock issued to the Lenders had not been exercised and were still outstanding. These warrants expire in December 2018. 2012 Private Placement Warrants In connection with the Private Placement, completed in June 2012, the Company issued PIPE warrants to purchase up to 2,630,103 shares of common stock. The per share exercise price of the PIPE warrants was $3.40 which equals the closing consolidated bid price of the Company ’s common stock on May 29, 2012, the effective date of the Purchase Agreement. The PIPE warrants issued in the Private Placement became exercisable six months after the issuance date, and expire on the five year anniversary of the initial exercisability date. Under the terms of the PIPE warrants, upon certain transactions, including a merger, tender offer, sale of all or substantially all of the assets of the Company or if a person or group shall become the owner of 50% of the Company’s issued and outstanding common stock, which is outside of the Company’s control, each PIPE warrant holder may elect to receive a cash payment in exchange for the warrant, in an amount determined by application of the Black-Scholes option-pricing model. Accordingly, the PIPE warrants were recorded as a liability at fair value, as determined by the Black-Scholes option-pricing model, and then marked to fair value each reporting period, with changes in estimated fair value recorded through the Consolidated Statements of Comprehensive Loss in interest income and other income (expense), net. The Black-Scholes assumptions used to value the PIPE warrants are disclosed in Note 2 “Investments and Fair Value Measurement.” Upon execution of the Purchase Agreement, the fair value of the PIPE warrants was estimated to be $5.8 million, w hich was recorded as a liability. The change in fair value for the years ended December 31, 2017, 2016 and 2015, which was recorded as other income, was $0.3 million, $0.6 million and $2.1 million, respectively. During the year ended December 31, 2017, 512,456 warrants expired unexercised. During the year ended December 31, 2015, PIPE warrants to purchase 847,058 shares were net exercised for 527,101 shares of common stock.

Warrants

Amended and Restated Loan Agreement

Warrants

In connection with the Original Loan Agreement, executed in

December 2013,

the Company issued warrants to the Lenders which were exercisable for an aggregate of

176,730

shares of common stock with an exercise price of

$6.79

per share, or the Warrants. In

connection with Amendment

No.

to the Original Loan Agreement, the Company reduced the exercise price of the warrants already held by the Lenders from the previous exercise price of

$6.79

per share to

$3.88

per share, or the First Warrant Amendments. In connection with Amendment

No.

to the Original Loan Agreement, the Company reduced the exercise price of the warrants already held by the Lenders from the previous exercise price of

$3.88

per share to

$3.07

per share, or the Second Warrant Amendments. Each Warrant

may

be exercised on a cashless basis. The Warrants are exercisable for a term beginning on the date of issuance and ending on the earlier to occur of

five

years from the date of issuance or the consummation of certain acquisitions of the Company as set forth in the Warrants. The number of shares for which the Warrants are exercisable and the associated exercise price are subject to certain proportional adjustments as set forth in the Warrants. The Company estimated the fair value of these Warrants as of the issuance date to be

$1.1

million, which was used in the estimating of the fair value of the amended debt instrument and was recorded as equity. The fair value of the Warrants was calculated using the Black-Scholes option-valuation model, and was based on the original strike price of

$6.79,

the stock price at issuance of

$9.67,

the

five

-year contractual term of the warrants, a risk-free interest rate of

1.55%,

expected volatility of

71%

and

expected dividend yield. The Company estimated the fair value of the modification of the First Warrant Amendments, as of the issuance date to be

$0.1

million, which was used in estimating the fair value of the amended debt instrument in

September 2015

and was recorded as equity, as well as the Second Warrant Amendments, which fair value was estimated to be

$45.0

thousand at the issuance date, and which was used in estimating the fair value of the amended debt instrument in

September 2016

and was recorded as equity.

As of

December 31, 2017,

warrants to purchase

176,730

shares of common stock issued to the Lenders had

not

been exercised and were still outstanding. These warrants expire in

December 2018.

2012

Private Placement Warrants

In connection with the Private Placement, completed in

June 2012,

the Company issued PIPE warrants to purchase up to

2,630,103

shares of common stock. The per share exercise price of the PIPE warrants was

$3.40

which equals the closing consolidated bid price of the Company

’s common stock on

May

29,

2012,

the effective date of the Purchase Agreement. The PIPE warrants issued in the Private Placement became exercisable

six

months after the issuance date, and expire on the

five

year anniversary of the initial exercisability date. Under the terms of the PIPE warrants, upon certain transactions, including a merger, tender offer, sale of all or substantially all of the assets of the Company or if a person or group shall become the owner of

50%

of the Company’s issued and outstanding common stock, which is outside of the Company’s control, each PIPE warrant holder

may

elect to receive a cash payment in exchange for the warrant, in an amount determined by application of the Black-Scholes option-pricing model. Accordingly, the PIPE warrants were recorded as a liability at fair value, as determined by the Black-Scholes option-pricing model, and then marked to fair value each reporting period, with changes in estimated fair value recorded through the Consolidated Statements of Comprehensive Loss in interest income and other income (expense), net. The Black-Scholes assumptions used to value the PIPE warrants are disclosed in Note

“Investments and Fair Value Measurement.”

Upon execution of the Purchase Agreement, the fair value of the PIPE warrants was estimated to be

$5.8

million, w

hich was recorded as a liability. The change in fair value for the years ended

December 31, 2017,

2016

and

2015,

which was recorded as other income, was

$0.3

million,

$0.6

million and

$2.1

million, respectively.

During the year ended

December 31,

2017,

512,456

warrants expired unexercised. During the year ended

December 31, 2015,

PIPE warrants to purchase

847,058

shares were net exercised for

527,101

shares of common stock.