Segment, Geographical and Other Revenue Information - Concentration Risk (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Concentration Risk [Line Items]
Revenue recognized	$ 14,967	$ 12,319	$ 29,637	$ 27,901
Nestec Ltd. (Nestle Health Sciences) [Member]
Concentration Risk [Line Items]
Revenue recognized	1,700	1,200	3,300	2,500
Nestec Ltd. (Nestle Health Sciences) [Member] | Global Development, Option and License Agreement [Member]
Concentration Risk [Line Items]
Revenue recognized	$ 0	$ 500	$ 0	$ 1,700
Revenue, Product and Service Benchmark [Member] | Customer Concentration Risk [Member] | Customer A [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	16.00%	35.00%	20.00%	38.00%
Revenue, Product and Service Benchmark [Member] | Customer Concentration Risk [Member] | Customer B [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	12.00%	14.00%	11.00%	26.00%
Revenue, Product and Service Benchmark [Member] | Customer Concentration Risk [Member] | Customer C [Member]
Concentration Risk [Line Items]
Concentration risk, percentage		11.00%
Revenue, Product and Service Benchmark [Member] | Customer Concentration Risk [Member] | Customer D [Member]
Concentration Risk [Line Items]
Concentration risk, percentage			13.00%
Revenue, Product and Service Benchmark [Member] | Customer Concentration Risk [Member] | Customer E [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	38.00%		27.00%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Customer A [Member]
Concentration Risk [Line Items]
Concentration risk, percentage			26.00%		38.00%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Customer B [Member]
Concentration Risk [Line Items]
Concentration risk, percentage			11.00%		10.00%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Customer D [Member]
Concentration Risk [Line Items]
Concentration risk, percentage			30.00%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Customer F [Member]
Concentration Risk [Line Items]
Concentration risk, percentage			10.00%