Schedule of Cash as Reported in Consolidated Statements of Cash Flows (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted Cash And Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 138,951,000	$ 181,568,000	$ 188,480,000
Restricted cash	1,062,000	173,000
Total cash balance in consolidated statements of cash flows	140,013,000	181,741,000	188,658,000	$ 186,829,000
SRX Cardio
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash	30,000	$ 173,000	$ 178,000
Royalty Payments | HealthCare Royalty Partners and its Affiliates (“HCR”)
Restricted Cash And Cash Equivalents Items [Line Items]
Restricted cash	$ 1,032,000