Investment in Silver Creek - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
	May 07, 2019	May 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Consolidation Less Than Wholly Owned Subsidiary Parent Ownership Interest Effects Of Changes Net [Line Items]
Equity method investment				$ 7,428
Loss on equity method investment			$ 372	(3,123)
Proceeds from sales and maturities of marketable securities			51,500	52,500
Equity method investment realized gain loss on sale			1,400
Silver Creek Pharmaceuticals, Inc. [Member]
Consolidation Less Than Wholly Owned Subsidiary Parent Ownership Interest Effects Of Changes Net [Line Items]
Equity method investment	$ 6,400			7,400
Loss on equity method investment			$ 1,000	$ 3,100
Proceeds from sales and maturities of marketable securities	$ 7,800	$ 7,800