Earnings Per Share - Components of Basic and Diluted Net Income Per Common Share (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Basic Net Income per Common Share Available to Common Stockholders:
Net income	$ 11,565,000	$ 11,670,000	$ 31,701,000	$ 35,967,000
Weighted average common shares outstanding	16,728,191	16,684,395	16,710,485	16,677,932
Basic earnings per common share	$ 0.69	$ 0.70	$ 1.90	$ 2.16
Diluted Net Income per Common Share Available to Common Stockholders:
Net income applicable to diluted earnings per share	$ 11,565,000	$ 11,670,000	$ 31,701,000	$ 35,967,000
Weighted average common shares outstanding	16,728,191	16,684,395	16,710,485	16,677,932
Dilutive potential common shares:
Restricted stock awarded	46,908	34,780	46,908	34,780
Dilutive potential common shares	46,908	34,780	46,908	34,780
Diluted weighted average common shares outstanding	16,775,099	16,719,175	16,757,393	16,712,712
Diluted earnings per common share	$ 0.69	$ 0.70	$ 1.89	$ 2.15