Dividends and Basic Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings per share for the period [Abstract]
Net Income	$ 6,749	$ 6,104	$ 13,152	$ 12,386
Weighted Average Number of Common Shares Outstanding (in shares)	785,782	777,882	785,575	777,882
Basic Earnings Per Common Share Amount (in dollars per share)	$ 8.59	$ 7.84	$ 16.74	$ 15.92
Mid-Year Cash Dividend 2015 [Member]
Dividends Payable [Line Items]
Dividends payable, date declared			May 18, 2015
Dividends on common stock (in dollars per share)			$ 6.40
Dividends payable, date of record			Jun. 09, 2015
Dividends payable, date paid			Jul. 01, 2015
Percentage increase in cash dividend per share (in hundredth)			1.60%
Mid-Year Cash Dividend 2014 [Member]
Dividends Payable [Line Items]
Dividends on common stock (in dollars per share)				$ 6.20
Dividends payable, date paid				Jul. 01, 2014