Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Net income (loss)	$ 582,542	$ 597,973	$ 579,150
Other comprehensive income (loss), before tax:
Change in net unrealized gain/loss on securities available for sale during the period	(171,662)	277,926	(2,143,567)
Change in net unrealized gain on securities transferred to held-to-maturity	(629)	(649)	(737)
Reclassification adjustment for net (gains) losses included in net income	96	(66)	0
Total securities available for sale and transferred securities before tax amount	(172,195)	277,211	(2,144,304)
Defined-benefit post-retirement benefit plans:
Change in the net actuarial gain/loss before tax amount	2,439	9,278	(5,005)
Reclassification adjustment for net amortization of actuarial gain/loss included in net income as a component of net periodic cost (benefit) before tax amount	1,673	3,479	2,964
Total defined-benefit post-retirement benefit plans	4,112	12,757	(2,041)
Reclassification adjustments for (gains) losses included in net income:
Other comprehensive income (loss), before tax	(168,083)	289,968	(2,146,345)
Deferred tax expense (benefit)	(35,298)	60,893	(450,733)
Other comprehensive income (loss), net of tax	(132,785)	229,075	(1,695,612)
Comprehensive income (loss)	$ 449,757	$ 827,048	$ (1,116,462)