Organization and Summary of Significant Accounting Policies - Initial and Secondary Public Offerings (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
	Jul. 22, 2015	Aug. 31, 2017	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Sales of common stock, (in shares)	5,500,000	5,175,000
Common stock, par value
Shares issued, price per share (in dollars per share)	$ 17.00	$ 23.00
Reclass from redeemable equity securities	$ 87,200	$ 113,100	$ 113,096