Casi Holdings and Evomela Supply Contract - Additional Information (Details) $ in Thousands, shares in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($) shares	Dec. 31, 2014 agreement	Dec. 31, 2019 USD ($)
Other Commitments [Line Items]
Equity securities	$ 20,497		$ 31,047
CASI out-license
Other Commitments [Line Items]
Number of agreements | agreement		3
Number of shares held in investment (shares) | shares	10.0
Percentage of ownership	10.00%
Equity securities	$ 20,500