Immaterial Restatement of Prior Period Financial Statements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Provision (benefit) for income taxes	$ 0	$ (8,216)
Loss from continuing operations	(40,617)	(39,846)
Income from discontinued operations, net of income taxes (Note 10)	45	20,587
Net loss	(40,572)	(19,259)
Total comprehensive loss	(41,901)	(19,649)
Accumulated deficit	$ (764,999)		$ (724,427)	$ (611,738)
As Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Provision (benefit) for income taxes		(8,242)
Loss from continuing operations		(39,820)
Income from discontinued operations, net of income taxes (Note 10)		20,665
Net loss		(19,155)
Total comprehensive loss		(19,545)
Accumulated deficit				$ 599,886
Adjustments for Error Corrections
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Provision (benefit) for income taxes		26
Loss from continuing operations		(26)
Income from discontinued operations, net of income taxes (Note 10)		(78)
Net loss		(104)
Total comprehensive loss		(104)
Pricing Of ZEVALIN to qualifying public health services | Adjustments for Error Corrections
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Error correction amount		$ 12,000