Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 84,407	$ 122,447	$ 149,346	$ 320,344
Other comprehensive income, before tax:
Change in unrealized holding gains on securities available for sale	(1,296)	29,085	76,815	168,592
Unrealized (loss) on transfer of securities held to maturity to available for sale	0	0	0	(11,813)
Reclassification adjustment for net realized (gains) losses included in net income	(642)	(6,882)	(9,539)	6,830
Accretion of net unrealized loss on securities transferred to held to maturity	131	119	288	2,658
Change in the actuarial loss of defined benefit plan and post-retirement benefit plans	779	(15,706)	(1,712)	(12,757)
Total other comprehensive (loss) income, before tax	(1,028)	6,616	65,852	153,510
Deferred tax benefit (expense) related to other comprehensive income	284	(1,828)	(18,202)	(42,431)
Other comprehensive (loss) income, net of tax	(744)	4,788	47,650	111,079
Comprehensive income	$ 83,663	$ 127,235	$ 196,996	$ 431,423