Summary of Significant Accounting Policies - Concentration of Revenue and Customers (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) item customer	Mar. 31, 2019 USD ($) item customer
Estimated total revenue from major customers
Number of geographical markets | item	2	2
Revenues	$ 36	$ 3,423
Revenue
Estimated total revenue from major customers
Number of customers | customer	1	1
Revenue | Roche Diabetes Care
Estimated total revenue from major customers
Percentage of total revenue	0.00%	59.00%
Revenue | Geographic Concentration Risk
Estimated total revenue from major customers
Percentage of total revenue	100.00%	100.00%
Revenues	$ 36	$ 3,423
Outside of the United States | Revenue | Geographic Concentration Risk
Estimated total revenue from major customers
Percentage of total revenue	33.30%	76.20%
Revenues	$ 12	$ 2,607
United States | Revenue | Geographic Concentration Risk
Estimated total revenue from major customers
Percentage of total revenue	66.70%	23.80%
Revenues	$ 24	$ 816