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Summary of Significant Accounting Policies - Summarized Unaudited Financial Information (Detail) (USD $)
In Thousands, unless otherwise specified |
3 Months Ended | 9 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|---|
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Sep. 30, 2013
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Sep. 30, 2012
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Sep. 30, 2013
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Sep. 30, 2012
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Dec. 31, 2012
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Dec. 31, 2011
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| Schedule of Equity Method Investments [Line Items] | ||||||
| Revenues | $ 6,133 | $ 2,925 | $ 16,890 | $ 7,269 | $ 13,925 | $ 8,171 |
| Operating expenses | 18,170 | 19,410 | 57,187 | 70,123 | 89,082 | 90,598 |
| Loss from operations | (12,037) | (16,485) | (40,297) | (62,854) | (75,157) | (82,427) |
| Net income (loss) | 14,991 | (20,490) | (27,890) | (50,937) | (81,874) | (85,280) |
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Ziopharm [Member]
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| Schedule of Equity Method Investments [Line Items] | ||||||
| Revenues | 200 | 200 | 600 | 600 | ||
| Operating expenses | 9,315 | 21,927 | 51,592 | 63,926 | ||
| Loss from operations | (9,115) | (21,727) | (50,992) | (63,326) | ||
| Other | (7,598) | 3,903 | 2,789 | (2,581) | ||
| Net income (loss) | $ (16,713) | $ (17,824) | $ (48,203) | $ (65,907) | ||