| **Unaudited Quarterly Results (unaudited)**            | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
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| **Unaudited Quarterly Results (unaudited) [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| Unaudited Quarterly Results (unaudited)                | 14. Unaudited Quarterly Results (unaudited)Summarized quarterly financial data during 2012 and 2011 are as follows:  2012 Quarter Ended   March 31  June 30  September 30  December 31 Revenues (1) $2,226  $1,820  $1,117  $8,885 Net loss  (13,086)  (10,720)  (11,301)  (324)Net loss per share - basic and diluted  (0.39)  (0.32)  (0.33)  (0.01)  2011 Quarter Ended   March 31  June 30  September 30  December 31 Revenues (2) $2,388  $74,407  $5,804  $2,197 Net income (loss)  (22,927)  55,486   (11,432)  (10,746)Net income (loss) per share - basic  (0.69)  1.66   (0.34)  (0.32)Net income (loss) per share - diluted  (0.69)  1.64   (0.34)  (0.32)_______________(1)Revenues in the fourth quarter of 2012 include $5.0 million and $2.8 million from the MedImmune and CytoDyn Agreements, respectively.(2)Revenues in the second quarter of 2011 include $59.5 million from the Salix Agreement |

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The entire disclosure for the quarterly financial data in the annual financial statements.  The disclosure may include a tabular presentation of financial information for each fiscal quarter for the current and previous year, including revenues, gross profit, income or loss before extraordinary items and earnings per share data. It also includes an indication if the information in the note is unaudited, comments on the aggregate effect of year-end adjustments, and an explanation of matters or transactions that affect comparability or are pertinent to an understanding of the information furnished.
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