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Selected Quarterly Financial Data (Details) (USD $)
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3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
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Dec. 31, 2014
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Sep. 30, 2014
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Jun. 30, 2014
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Mar. 31, 2014
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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, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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| Statements of Operations and Comprehensive Loss | |||||||||||
| Net loss | $ (17,962,000) | $ (17,420,000) | $ (12,609,000) | $ (14,488,000) | $ (12,531,000) | $ (20,342,000) | $ (19,512,000) | $ (8,305,000) | $ (62,479,000) | $ (60,690,000) | $ (69,128,000) |
| Net loss applicable to common stock | (17,962,000) | (17,420,000) | (16,640,000) | (19,457,000) | (17,304,000) | (25,090,000) | (23,880,000) | (11,887,000) | (71,479,000) | (78,161,000) | (83,120,000) |
| Net loss per share - basic and diluted | $ (0.55) | $ (0.59) | $ (2.22) | $ (50.45) | $ (44.87) | $ (65.05) | $ (62.59) | $ (31.25) | |||
| Weighted-average common shares outstanding - basic and diluted | 32,678,459 | 29,746,426 | 7,500,148 | 385,664 | 385,688 | 385,688 | 381,525 | 380,352 | 17,699,487 | 383,310 | 368,261 |