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