Development and License Agreements - Summary of Amounts Payable and Amounts Receivable from Fresenius (Detail) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Related Party Transactions [Abstract]
Payables to Fresenius	[1]	$ 7,507	$ 7,812
Receivables from Fresenius	[2]	$ 954	$ 1,777

[1] Included in “Accounts Payable” and “Accrued Liabilities” in the Company's condensed consolidated balance sheets.

[2] Included in “Other current assets” in the Company's condensed consolidated balance sheets