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Joint Venture - Additional Information (Detail) - USD ($) $ in Millions	Jul. 05, 2019	Sep. 30, 2019	Jan. 03, 2019	Dec. 31, 2018
Subsidiary or Equity Method Investee [Line Items]
Common stock, shares issued		181,030,020		161,066,136
Eden Bio Cell [Member]
Subsidiary or Equity Method Investee [Line Items]
Equity method investments		$ 0.0
Ziopharm [Member] \| Eden Bio Cell [Member]
Subsidiary or Equity Method Investee [Line Items]
Equity interest in affilated entity	50.00%
Tri Arm [Member] \| Eden Bio Cell [Member]
Subsidiary or Equity Method Investee [Line Items]
Equity interest in affilated entity	50.00%
Tri Arm [Member] \| License Agreement Terms [Member] \| Eden Bio Cell [Member]
Subsidiary or Equity Method Investee [Line Items]
Milestone payment made	$ 10.0
Conditional milestone amount payable	$ 25.0
Share Subscription Agreement [Member] \| Ziopharm [Member] \| Eden Bio Cell [Member]
Subsidiary or Equity Method Investee [Line Items]
Common stock, shares issued			10,000,000
Share Subscription Agreement [Member] \| Tri Arm [Member] \| Eden Bio Cell [Member]
Subsidiary or Equity Method Investee [Line Items]
Common stock, shares issued			10,000,000