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Taxes
 6 Months Ended
Jun. 30, 2017
Taxes [Abstract]  
Taxes
(7) Taxes:
As of June 30, 2017, the Company's calendar years 2016, 2015 and 2014 remain subject to examination by the Internal Revenue Service.  The effective federal income tax rate differs from the normal statutory rate primarily as a result of tax-exempt investment income.