Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 42,341	$ 44,124
Debt securities available-for-sale:
Net change in unrealized gains (losses) on debt securities available-for-sale	36,610	(139,854)
Related income tax (expense) benefit	(8,782)	33,607
Net securities losses reclassified into earnings	151	2
Related income tax benefit	(37)	(1)
Net effect on other comprehensive income for the period	27,942	(106,246)
Defined benefit plans:
Amortization of net loss and prior service costs	98	72
Related income tax benefit	(23)	(18)
Net effect on other comprehensive income for the period	75	54
Total other comprehensive gain (loss)	28,017	(106,192)
Comprehensive income (loss)	$ 70,358	$ (62,068)