Organization and Summary of Significant Accounting Policies - Use of Estimates (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
Organization, Consolidation and Presentation of Financial Statements [Abstract] | |||
Gain on contribution to equity method investment | $ 68,000 | $ 0 | $ 0 |