Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income per consolidated statements of income	$ 71,887	$ 147,365	$ 160,025
Net unrealized gains (losses) on available for sale securities and transferred securities:
Net unrealized holding gains (losses) arising during the period	(172,143)	(37,090)	22,965
Change in net unrealized holding loss on securities transferred to held to maturity	(64,525)	1,985	2,383
Pension and other postretirement benefit plans:
Change in the actuarial loss of pension and other postretirement benefit plans	8,094	2,134	(3,846)
Reclassification adjustments for changes realized in net income:
Net change in prior service costs	83	84	112
Recognized net loss due to lump sum settlements	0	137	89
Change in net actuarial loss	817	1,241	846
Derivatives:
Change in the accumulated gain (loss) on effective cash flow hedge derivatives	(15,514)	0	0
Reclassification adjustment for (gain) loss realized in net income	345	0	0
Other comprehensive income (loss), net of tax	(242,843)	(31,509)	22,549
Comprehensive income	$ (170,956)	$ 115,856	$ 182,574