Earnings per Share (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings per share basic and diluted [Abstract]
Net income applicable to common stock	$ 4,581,000	$ 3,650,000	$ 13,519,000	$ 10,421,000
Basic earnings per share computation [Abstract]
Weighted average common shares outstanding (in shares)	3,502,859	3,517,208	3,507,515	3,515,032
Earnings per share - basic (in dollars per share)	$ 1.31	$ 1.04	$ 3.85	$ 2.96
Diluted earnings per share computation [Abstract]
Weighted average common shares outstanding for basic earnings per share (in shares)	3,502,859	3,517,208	3,507,515	3,515,032
Add: Dilutive effects of restricted stock (in shares)	161	2,285	2,161	1,874
Weighted average common shares outstanding for dilutive earnings per share (in shares)	3,503,020	3,519,493	3,509,676	3,516,906
Earnings per share - diluted (in dollars per share)	$ 1.31	$ 1.04	$ 3.85	$ 2.96
Restricted Stock [Member]
Antidilutive Securities [Abstract]
Antidilutive restricted stock excluded from net income per share calculations (in shares)	4,696	1,107	4,033	4,162
Restricted Stock [Member] | Minimum [Member]
Antidilutive Securities [Abstract]
Antidilutive stock share price range (in dollars per share)	$ 46.69	$ 49.87	$ 46.69	$ 46.69
Restricted Stock [Member] | Maximum [Member]
Antidilutive Securities [Abstract]
Antidilutive stock share price range (in dollars per share)	$ 62.93	$ 53.15	$ 61.04	$ 53.15