Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net Income	$ 8,734	$ 8,531
Other Comprehensive Income (Loss), Net of Tax:
Net Unrealized Securities Holding Gains (Losses) Arising During the Period	2,080	(2,485)
Amortization of Net Retirement Plan Actuarial Loss	121	46
Amortization (Accretion) of Net Retirement Plan Prior Service Cost (Credit)	42	(1)
Other Comprehensive Income (Loss)	2,243	(2,440)
Comprehensive Income	$ 10,977	$ 6,091