Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 129,582	$ 79,356	$ 325,472	$ (148,749)
Other comprehensive income (loss) before income taxes:
Net change in unrealized gain or loss on securities available for sale and cash flow hedges	(48,569)	425	(143,924)	217,254
Reclassification of net income realized and included in earnings	(6,425)	(4,076)	(9,337)	(6,593)
Valuation adjustments to pension plan attributable to the Voluntary Early Retirement Incentive Program (VERIP) and curtailment			59,606
Other valuation adjustments to employee benefit plans			(10,651)	(10,251)
Amortization of unrealized net gain on securities transferred to held to maturity	(33)	(89)	(134)	(378)
Other comprehensive income (loss) before income taxes	(55,027)	(3,740)	(104,440)	200,032
Income tax expense (benefit)	(12,363)	48	(24,569)	46,370
Other comprehensive income (loss) net of income taxes	(42,664)	(3,788)	(79,871)	153,662
Comprehensive income	$ 86,918	$ 75,568	$ 245,601	$ 4,913