Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 104,131	$ 146,936	$ 95,644
Unrealized gains (losses) on securities available for sale:
Unrealized holding gains (losses) arising during the period, pretax	43,343	(411,996)	(53,752)
Tax (expense) benefit	(9,279)	94,677	12,352
Reclassification to realized losses	0	0	1,237
Tax benefit	0	0	(284)
Postretirement plans:
Net (gains) losses arising during period	(607)	695	872
Tax expense (benefit)	141	(159)	(201)
Amortization of unrecognized net actuarial (gains) losses	(545)	(288)	592
Tax expense (benefit)	126	66	(136)
Recognition of net actuarial loss due to plan settlement	998	0	0
Tax benefit	(232)	0	0
Other comprehensive income (loss)	33,945	(317,005)	(39,320)
Comprehensive income (loss)	$ 138,076	$ (170,069)	$ 56,324