Organization and Summary of Significant Accounting Policies - Initial Public Offering (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended	12 Months Ended
	Dec. 09, 2015	Jan. 30, 2014	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Common stock, shares outstanding					20,058,904	20,876,837
IPO [Member]
Class of Stock [Line Items]
Common stock, shares outstanding		16,448,750
Common Stock [Member] | IPO [Member]
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs, shares		8,984,375
Share Price (in dollars per share)		$ 11.00
Repurchase of common stock, shares			1,171,875
Net proceeds from issuance of common stock, net of underwriting discount, offering expenses and repurchase or shares			$ 75.8
Common Stock [Member] | Over-Allotment Option [Member]
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs, shares	525,000	1,171,875
Common Stock [Member] | Follow-on offering [Member]
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs, shares	4,025,000
Share Price (in dollars per share)	$ 12.50
Net proceeds from issuance of common stock, net of underwriting discount, offering expenses and repurchase or shares				$ 47.3
Common stock, shares outstanding	20,541,546