Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net income	$ 21,036	$ 18,172	$ 64,822	$ 53,335
Weighted average shares outstanding - basic and diluted (in shares)	5,114,701	5,113,077	5,113,877	5,112,108
Net income per common share- basic and diluted (in dollars per share)	$ 4.11	$ 3.55	$ 12.68	$ 10.43