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Taxes
 3 Months Ended
Mar. 31, 2017
Taxes [Abstract]  
Taxes
(7)Taxes:
As of March 31, 2017, the Company's calendar years 2016, 2015 and 2014 remain subject to examination by the IRS.  The effective federal income tax rate differs from the normal statutory rate primarily as a result of tax-exempt investment income.