Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income per consolidated statements of income	$ 165,489	$ 71,887	$ 147,365
Net unrealized gains (losses) on available for sale securities and transferred securities:
Net unrealized holding gains (losses) arising during the period	38,133	(172,143)	(37,090)
Reclassification adjustment for net (gains) losses realized in net income	(29)	0	0
Change in net unrealized holding loss on securities transferred to held to maturity	11,668	(64,525)	1,985
Pension and other postretirement benefit plans:
Change in the actuarial loss of pension and other postretirement benefit plans	(518)	8,094	2,134
Reclassification adjustments for changes realized in net income:
Net change in prior service costs	83	83	84
Recognized net loss due to lump sum settlements	19	0	137
Change in net actuarial loss	133	817	1,241
Derivatives:
Change in the accumulated gain (loss) on effective cash flow hedge derivatives	(6,098)	(15,514)	0
Reclassification adjustment for (gain) loss realized in net income	12,289	345	0
Other comprehensive income (loss), net of tax	55,680	(242,843)	(31,509)
Comprehensive income (loss)	$ 221,169	$ (170,956)	$ 115,856