Schedule of Changes In Each Component of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Three months ended March 31,
Beginning Balance	$ 657,983	$ 600,764
Other comprehensive income	21,620	8,631
Ending balance	685,228	619,241
Defined Benefit Pension Plans
Three months ended March 31,
Beginning Balance	(6,270)	(5,871)
Ending balance	(6,270)	(5,871)
Unrealized Gain (Losses) on Securities Available-for-Sale
Three months ended March 31,
Beginning Balance	12,110	(8,611)
Other comprehensive income before reclassifications	20,471	8,698
Amounts reclassified from other comprehensive loss	(48)	(67)
Reclassification of unrealized gains on held-to-maturity securities to available-for-sale	1,197
Other comprehensive income	21,620	8,631
Ending balance	33,730	20
Accumulated Other Comprehensive Income (Loss)
Three months ended March 31,
Beginning Balance	5,840	(14,482)
Other comprehensive income before reclassifications	20,471	8,698
Amounts reclassified from other comprehensive loss	(48)	(67)
Reclassification of unrealized gains on held-to-maturity securities to available-for-sale	1,197
Other comprehensive income	21,620	8,631
Ending balance	$ 27,460	$ (5,851)