Organization and Summary of Significant Accounting Policies - Liquidity - Financial Statement Disclosures (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Organization Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 30,078	$ 19,719	$ 23,089	$ 5,972
Accumulated deficit	$ 99,844	$ 94,156