Per Share Data (Computation of Basic Earnings Per Share and Diluted Earnings Per Share) (Details) $ / shares in Units, $ in Thousands			3 Months Ended								12 Months Ended
		Apr. 21, 2017	Dec. 31, 2017 USD ($) $ / shares	Sep. 30, 2017 USD ($) $ / shares	Jun. 30, 2017 USD ($) $ / shares	Mar. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($) $ / shares	Sep. 30, 2016 USD ($) $ / shares	Jun. 30, 2016 USD ($) $ / shares	Mar. 31, 2016 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares shares		Dec. 31, 2016 USD ($) $ / shares shares		Dec. 31, 2015 USD ($) $ / shares shares
Basic Earnings per Share:(1)
Net Income | $			$ 11,621	$ 9,660	$ 9,839	$ 9,556	$ 10,065	$ 10,185	$ 9,788	$ 5,146	$ 40,676		$ 35,184		$ 30,064
Weighted Average Shares Outstanding (in shares)	[1]										22,924,726		22,389,137		19,882,503
Basic Earnings per Share (in USD per share) | $ / shares			$ 0.51	$ 0.42	$ 0.43	$ 0.42	$ 0.44	$ 0.45	$ 0.43	$ 0.25	$ 1.77	[1],[2]	$ 1.57	[1],[2]	$ 1.51	[1],[2]
Diluted Earnings per Share:
Net Income | $			$ 11,621	$ 9,660	$ 9,839	$ 9,556	$ 10,065	$ 10,185	$ 9,788	$ 5,146	$ 40,676		$ 35,184		$ 30,064
Weighted Average Shares Outstanding (in shares)	[1]										22,924,726		22,389,137		19,882,503
Stock Options, Net (in shares)	[1]										0		1,979		5,871
Diluted Weighted Average Shares Outstanding (in shares)	[1]										22,924,726		22,391,116		19,888,374
Diluted Earnings per Share (in USD per share) | $ / shares			$ 0.51	$ 0.42	$ 0.43	$ 0.42	$ 0.44	$ 0.45	$ 0.43	$ 0.25	$ 1.77	[1],[2]	$ 1.57	[1],[2]	$ 1.51	[1],[2]
Antidilutive securities excluded from computation of earnings per share (in shares)											0		0		0
Stock split conversion ratio		1.50

[1] Share and per share data has been adjusted to reflect a 3-for-2 stock split on April 21, 2017.

[2] Per share data has been adjusted to reflect a 3-for-2 stock split on April 21, 2017.