Investment in Preferred Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Noncash dividend income on preferred shares		$ 7,421	$ 0	$ 0
ZIOPHARM Oncology, Inc.
Schedule of Investments [Line Items]
Preferred shares, stated value (in usd per share)	$ 1,200
Threshold consecutive trading days, conversion in shares		20 days
Preferred shares, dividend rate (in usd per share)		$ 12.00
Preferred shares, dividend rate, for unconverted shares after conversion event (in usd per share)		24.00
Minimum | ZIOPHARM Oncology, Inc.
Schedule of Investments [Line Items]
Preferred shares, conversion calculation, divisor (in usd per share)		$ 1.00
ZIOPHARM Oncology, Inc.
Schedule of Investments [Line Items]
Dividend income, number of preferred shares received (in shares)		6,184
Other Contractual Payments | Upfront and Milestone Payments | ZIOPHARM Oncology, Inc.
Schedule of Investments [Line Items]
Collaborative arrangement consideration received, number of preferred shares (in shares)	100,000