Business and Basis of Presentation (Additional Information) (Details) - USD ($)	Aug. 07, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents		$ 18,073,000	$ 18,100,000	$ 18,083,000	$ 19,590,000	$ 29,730,000
Debt instrument, covenant, compensating cash balance			13,200,000
Senior Secured Debentures
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Debt instrument, face amount			$ 25,500,000.0
Galena Biopharma, Inc | Subsequent Event
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Ownership percentage by Parent	32.50%
Galena Biopharma, Inc | SELLAS | Subsequent Event
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Percentage of voting interests acquired	67.50%
Out-Of-The-Money Warrants | Subsequent Event
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Number of shares availabe from warrants	2,556,851
Funding NeuVax in 2019 | Subsequent Event
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Funding commitment in 2019	$ 3,000,000