Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 36,842	$ 53,033	$ 124,064	$ 139,903
Debt securities available-for-sale:
Net change in unrealized losses on debt securities available-for-sale	(44,112)	(119,299)	(47,521)	(344,480)
Related income tax effect	10,705	28,665	11,632	82,787
Net securities losses reclassified into earnings	69		228	10
Related income tax effect	(17)		(55)	(2)
Net effect on other comprehensive income for the period	(33,355)	(90,634)	(35,716)	(261,685)
Defined benefit plans:
Amortization of net loss and prior service costs	100	73	298	218
Related income tax effect	(24)	(18)	(72)	(53)
Net effect on other comprehensive income for the period	76	55	226	165
Total other comprehensive loss	(33,279)	(90,579)	(35,490)	(261,520)
Comprehensive income (loss)	$ 3,563	$ (37,546)	$ 88,574	$ (121,617)