Annual report pursuant to Section 13 and 15(d)

Organization and summary of significant accounting policies (Cash, cash equivalents and short-term investments) (Details)

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Organization and summary of significant accounting policies (Cash, cash equivalents and short-term investments) (Details) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Accounts Receivable, Net, Current [Abstract]    
Cash and cash equivalent investment portfolio, percentage 41.00% 9.00%
Management fees $ 21,897 $ 29,549