Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings per share basic and diluted [Abstract]
Net income applicable to common stock	$ 3,650	$ 3,153	$ 10,421	$ 9,467
Basic earnings per share computation [Abstract]
Weighted average common shares outstanding (in shares)	3,482,936	3,505,526	3,480,760	3,512,187
Earnings per share - basic (in dollars per share)	$ 1.05	$ 0.90	$ 2.99	$ 2.70
Diluted earnings per share computation [Abstract]
Weighted average common shares outstanding for basic earnings per share (in shares)	3,482,936	3,505,526	3,480,760	3,512,187
Add: Dilutive effects of restricted stock (in shares)	2,285	1,694	1,874	1,698
Weighted average common shares outstanding for dilutive earnings per share (in shares)	3,485,221	3,507,220	3,482,634	3,513,885
Earnings per share - diluted (in dollars per share)	$ 1.05	$ 0.90	$ 2.99	$ 2.69
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive restricted stock excluded from net income per share calculations (in shares)	1,107	3,804	4,162	3,804
Restricted Stock [Member] | Minimum [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive stock share price range (in dollars per share)	$ 49.87	$ 46.69	$ 46.69	$ 46.69
Restricted Stock [Member] | Maximum [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive stock share price range (in dollars per share)	$ 53.15	$ 53.15	$ 53.15	$ 53.15