Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	$ 151,510	$ 159,032	$ 192,113
Debt securities available-for-sale:
Net change in unrealized gains (losses) on debt securities available-for-sale	12,511	38,535	(339,422)
Related income tax effect	(2,835)	(10,045)	82,253
Net securities losses reclassified into earnings	12	241	13
Related income tax effect	(236)	(58)	(3)
Net effect on other comprehensive income (loss) for the period	9,452	28,673	(257,159)
Defined benefit plans:
Amortization of net (gain) loss and prior service costs	(406)	399	291
Related income tax effect	122	(97)	(70)
Recognition of unrealized gain (loss)	845	8,909	(473)
Related income tax effect	(203)	(2,161)	115
Gain on settlement of retired employee accounts	(2,301)
Related income tax effect	552
Net effect on other comprehensive (loss) income for the period	(1,391)	7,050	(137)
Total other comprehensive income (loss)	8,061	35,723	(257,296)
Comprehensive income (loss)	$ 159,571	$ 194,755	$ (65,183)