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Selected Quarterly Financial Data (Detail) (USD $)
In Thousands, except Per Share data, unless otherwise specified |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
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Dec. 31, 2013
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Sep. 30, 2013
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Jun. 30, 2013
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Mar. 31, 2013
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Dec. 31, 2012
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Sep. 30, 2012
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Jun. 30, 2012
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Mar. 31, 2012
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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| Selected Quarterly Financial Data [Line Items] | |||||||||||
| Revenues | $ 2,847 | $ 2,927 | $ 3,392 | $ 2,085 | $ 1,806 | $ 2,874 | $ 2,684 | $ 2,350 | $ 11,251 | $ 9,714 | $ 21,614 |
| Net loss | (13,056) | (15,675) | (17,164) | (20,825) | (20,543) | (17,791) | (15,110) | (16,505) | (66,720) | (69,949) | (48,597) |
| Net loss allocable to common stockholders | $ (21,525) | $ (15,675) | $ (17,164) | $ (20,825) | $ (20,543) | $ (17,791) | $ (15,110) | $ (16,505) | $ (75,189) | $ (69,949) | $ (48,597) |
| Basic and diluted net loss per share allocable to common stockholders | $ (0.09) | $ (0.09) | $ (0.09) | $ (0.11) | $ (0.11) | $ (0.10) | $ (0.09) | $ (0.11) | $ (0.38) | $ (0.41) | $ (0.39) |
| Weighted-average common shares outstanding | 235,879 | 183,022 | 182,913 | 182,847 | 180,685 | 177,870 | 167,697 | 155,431 | 196,275 | 170,469 | 125,101 |