Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Net income (loss)	$ 648,557	$ 582,542	$ 597,973
Other comprehensive income (loss), before tax:
Change in net unrealized gain/loss on securities available for sale during the period	514,556	(171,662)	277,926
Change in net unrealized gain on securities transferred to held-to-maturity	(521)	(629)	(649)
Reclassification adjustment for net (gains) losses included in net income	850	96	(66)
Total securities available for sale and transferred securities before tax amount	514,885	(172,195)	277,211
Defined-benefit post-retirement benefit plans:
Change in the net actuarial gain/loss before tax amount	1,665	2,439	9,278
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) before tax amount	1,239	1,673	3,479
Total defined-benefit post-retirement benefit plans	2,904	4,112	12,757
Reclassification adjustments for (gains) losses included in net income:
Other comprehensive income (loss), before tax	517,789	(168,083)	289,968
Deferred tax expense (benefit)	108,736	(35,298)	60,893
Other comprehensive income (loss), net of tax	409,053	(132,785)	229,075
Comprehensive income (loss)	$ 1,057,610	$ 449,757	$ 827,048