Casi Holdings and Evomela Supply Contract - Additional Information (Details) $ in Thousands, shares in Millions	1 Months Ended		3 Months Ended
	Apr. 30, 2019 shares	Sep. 30, 2014 agreement	Mar. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($)
Other Commitments [Line Items]
Equity securities | $			$ 33,142	$ 46,422
CASI Out-License [Member]
Other Commitments [Line Items]
Number of agreements | agreement		3
Number of shares held in investment (shares) | shares			11.5
Percentage of ownership			12.10%
Equity securities | $			$ 33,100
Subsequent Event [Member] | CASI Out-License [Member]
Other Commitments [Line Items]
Number of shares sold (shares) | shares	1.5