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	$ 29,893	$ 37,949	$ 74,457	$ 108,503
Unrealized losses on securities available for sale:
Unrealized losses arising during the period	(81,515)	(141,155)	(77,597)	(432,573)
Tax benefit	18,871	32,437	18,719	99,405
Postretirement Plans:
Amortization of unrecognized net actuarial loss	44	44	132	132
Tax expense	(10)	(10)	(31)	(30)
Other comprehensive loss	(62,610)	(108,684)	(58,777)	(333,066)
Comprehensive (loss) income	$ (32,717)	$ (70,735)	$ 15,680	$ (224,563)