Description of Business - Textual (Details) - Nestec Ltd. (Nestle Health Sciences) [Member] - CDX-6114 [Member] - Collaborative Arrangement [Member] - USD ($) $ in Millions	1 Months Ended	3 Months Ended
Feb. 28, 2019	Dec. 31, 2018	Mar. 31, 2019
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payment amount		$ 1.0	$ 1.0
Duration to pay after milestone achievement		60 days	60 days
Event of counterparty exercising alternative option	$ 3.0

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration