Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 15,161	$ 33,969
Unrealized gains (losses) on securities available for sale:
Unrealized gains (losses) arising during the period	35,333	(181,795)
Tax (expense) benefit	(7,425)	41,776
Postretirement Plans:
Amortization of unrecognized net actuarial loss	44	44
Tax benefit	(11)	(10)
Other comprehensive income (loss)	27,941	(139,985)
Comprehensive income (loss)	$ 43,102	$ (106,016)