Per Share Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Basic Earnings per Share:
Net Income	$ 10,980	$ 12,639	$ 11,097	$ 11,813	$ 11,621	$ 9,660	$ 9,839	$ 9,556	$ 46,529	$ 40,676	$ 35,184
Weighted Average Shares Outstanding (in shares)									23,381,616	22,924,726	22,389,137
Basic Earnings per Share (in USD per share)	$ 0.44	$ 0.55	$ 0.48	$ 0.51	$ 0.51	$ 0.42	$ 0.43	$ 0.42	$ 1.99	$ 1.77	$ 1.57
Diluted Earnings per Share:
Net Income	$ 10,980	$ 12,639	$ 11,097	$ 11,813	$ 11,621	$ 9,660	$ 9,839	$ 9,556	$ 46,529	$ 40,676	$ 35,184
Weighted Average Shares Outstanding (in shares)									23,381,616	22,924,726	22,389,137
Stock Options, Net (in shares)									0	0	1,978
Diluted Weighted Average Shares Outstanding (in shares)									23,381,616	22,924,726	22,391,115
Diluted Earnings per Share (in USD per share)	$ 0.44	$ 0.55	$ 0.48	$ 0.51	$ 0.51	$ 0.42	$ 0.43	$ 0.42	$ 1.99	$ 1.77	$ 1.57
Antidilutive securities excluded from computation of earnings per share (in shares)									0	0	0
Stock options outstanding (in shares)	0				0				0	0	0