Accounts Payable, Accrued Expenses and Other - Schedule of Accounts Payable, Accrued Expenses and Other (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts Payable And Accrued Liabilities [Line Items]
Accounts payable	$ 2,887	$ 2,692
Accrued goods and services	5,663	7,534
Accrued clinical trial costs	3,901	8,776
Accrued drug purchase costs	222	480
Accrued payroll and related benefits	2,884	3,394
Accrued restructuring expenses	628	774
Accrued interest		2,100
Accrued dividends payable	19	19
Deferred tax incentives	1,402	1,402
Total accounts payable, accrued expenses and other	$ 17,606	28,670
Silver Creek [Member]
Accounts Payable And Accrued Liabilities [Line Items]
Warrant liability		$ 1,499