Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 27,249	$ 21,338
Other comprehensive income (loss), net of taxes:
Change in total obligation for postretirement benefits and for prior service credit and for other benefits	43	48
Net unrealized gains (losses) on securities:
Unrealized holding gains (losses) on securities available for sale	6,402	12,099
Reclassification adjustment for losses realized in income	2,774	3,086
Accretion of net unrealized loss on securities transferred to held-to-maturity	595	488
Net unrealized gains (losses) on securities	9,771	15,673
Other comprehensive income, before tax	9,814	15,721
Income tax expense	(2,682)	(4,331)
Total other comprehensive income, net of taxes	7,132	11,390
Total comprehensive income, net of taxes	$ 34,381	$ 32,728