Organization and Significant Accounting Policies - Adoption of Revenue Recognition Standard Impacted Previously Reported Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue, current portion	$ 4,401	$ 2,631
Deferred revenue, net of current portion	2,566	5,946
Accumulated deficit	$ (172,327)	(159,654)
ASU 2014-09 (Topic 606)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue, current portion		467
Deferred revenue, net of current portion		(973)
Accumulated deficit		506
Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred revenue, current portion		2,164
Deferred revenue, net of current portion		6,919
Accumulated deficit		$ (160,160)