Business Combination - Schedule of Preliminary and Final Allocation of Purchase Consideration (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	$ 13,064	$ 13,064		$ 16,864
Adjustment
Adjustment		(14,600)	$ 0
Viventia Bio, Inc.
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Cash and cash equivalents	136	136		136
Prepaid expenses and other assets	1,162	1,162		1,162
Property and equipment	867	867		867
In-process research and development assets (all markets)	46,400	46,400		60,500
Goodwill	13,064	13,064		16,864
Accounts payable	(1,163)	(1,163)		(1,163)
Accrued expenses	(2,001)	(2,001)		(1,494)
Other liabilities	(812)	(812)		(812)
Deferred tax liability	(12,528)	(12,528)		(16,335)
Recognized identifiable assets acquired, goodwill, and liabilities assumed, net	45,125	$ 45,125		$ 59,725
Adjustment
Cash and cash equivalents	0
Prepaid expenses and other assets	0
Property and equipment	0
In-process research and development assets (all markets)	(14,100)
Goodwill	(3,800)
Accounts payable	0
Accrued expenses	(507)
Other liabilities	0
Deferred tax liability	3,807
Adjustment	$ (14,600)