Description of Business Description of Business (Details) - CDX-6114 - Nestec Ltd. (Nestle Health Sciences) - Collaborative Arrangement - USD ($) $ in Millions	1 Months Ended
	Feb. 28, 2019	Dec. 31, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payment amount		$ 1.0
Duration to pay after milestone achievement		60 days
Subsequent Event
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount from exercising alternative option	$ 3.0
Duration to pay after license effective date	60 days
Threshold to achieve aggregate milestone amount	$ 1,000.0
Subsequent Event | Development and Approval
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Maximum milestone receivable	86.0
Subsequent Event | Sales-based Milestone
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Maximum milestone receivable	$ 250.0