Common Stock - Components of Stock-Based Compensation Expense (Detail) (USD $)
In Thousands, unless otherwise specified |
6 Months Ended | 84 Months Ended | |
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Jun. 30, 2013
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Jun. 30, 2012
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Jun. 30, 2013
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
Total stock-based compensation expense | $ 2,806 | $ 1,218 | $ 10,318 |
Employee Awards [Member]
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
Total stock-based compensation expense | 2,016 | 812 | 5,222 |
Non-Employee Awards [Member]
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
Total stock-based compensation expense | 652 | 242 | 4,065 |
Non-Employee Warrants [Member]
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
Total stock-based compensation expense | $ 138 | $ 164 | $ 1,031 |