Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 57,203	$ 53,071	$ 28,476
Other comprehensive income (loss):
Net change in unrealized gains (losses) on available-for-sale securities, net of tax	21,076	(7,993)	(2,444)
Net change in unrealized losses on cash flow hedging derivatives, net of tax	(1,611)	1,489	787
Net (loss) gain on postretirement plans, net of tax	1,313	(1,831)	1,172
Other comprehensive income (loss)	18,152	(4,673)	(2,829)
Comprehensive income	$ 75,355	$ 48,398	$ 25,647