Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Narrative (Details)

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Summary of Significant Accounting Policies - Narrative (Details) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Accounting Policies [Abstract]    
Investments with fair value below carrying value or in an unrealized loss position $ 0  
Allowance for doubtful accounts 0 $ 0
Impairment of long-lived assets $ 0