Fair Value of Financial Assets and Liabilities, Allocated into Level 1, Level 2, and Level 3 Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financial Assets:
Total financial assets	$ 295,849	$ 515,458
Money market funds
Financial Assets:
Total financial assets	19,500	31,836
Corporate notes and commercial paper
Financial Assets:
Total financial assets	166,159	313,164
U.S. Treasury bills and government agency securities
Financial Assets:
Total financial assets	110,190	170,458
Liability-classified Lonza award
Financial Liabilities:
Total financial liabilities	9,200
Consolidarted Entities Excluding SRX Cardio
Financial Assets:
Total financial assets	295,849	515,458
Financial Liabilities:
Total financial liabilities	11,698
Consolidarted Entities Excluding SRX Cardio | Money market funds
Financial Assets:
Total financial assets	19,500	31,836
Consolidarted Entities Excluding SRX Cardio | Corporate notes and commercial paper
Financial Assets:
Total financial assets	166,159	313,164
Consolidarted Entities Excluding SRX Cardio | U.S. Treasury bills and government agency securities
Financial Assets:
Total financial assets	110,190	170,458
Consolidarted Entities Excluding SRX Cardio | Embedded derivative liabilities
Financial Liabilities:
Total financial liabilities	2,497	8,854
Consolidarted Entities Excluding SRX Cardio | Liability-classified Lonza award
Financial Liabilities:
Total financial liabilities	9,201
Consolidarted Entities Excluding SRX Cardio | Fair Value, Inputs, Level 1
Financial Assets:
Total financial assets	19,500	31,836
Consolidarted Entities Excluding SRX Cardio | Fair Value, Inputs, Level 1 | Money market funds
Financial Assets:
Total financial assets	19,500	31,836
Consolidarted Entities Excluding SRX Cardio | Fair Value, Inputs, Level 2
Financial Assets:
Total financial assets	276,349	483,622
Consolidarted Entities Excluding SRX Cardio | Fair Value, Inputs, Level 2 | Corporate notes and commercial paper
Financial Assets:
Total financial assets	166,159	313,164
Consolidarted Entities Excluding SRX Cardio | Fair Value, Inputs, Level 2 | U.S. Treasury bills and government agency securities
Financial Assets:
Total financial assets	110,190	170,458
Consolidarted Entities Excluding SRX Cardio | Fair Value, Inputs, Level 3
Financial Liabilities:
Total financial liabilities	11,698
Consolidarted Entities Excluding SRX Cardio | Fair Value, Inputs, Level 3 | Embedded derivative liabilities
Financial Liabilities:
Total financial liabilities	2,497	$ 8,854
Consolidarted Entities Excluding SRX Cardio | Fair Value, Inputs, Level 3 | Liability-classified Lonza award
Financial Liabilities:
Total financial liabilities	$ 9,201