Earnings Per 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 [Abstract]
Net income	$ 17,341	$ 16,828	$ 35,163	$ 32,072
Weighted average shares outstanding- basic and diluted (in shares)	5,112,026	5,110,369	5,111,616	5,110,045
Net income per common share- basic and diluted (in dollars per share)	$ 3.39	$ 3.29	$ 6.88	$ 6.28