Other Comprehensive Income - Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Mar. 31, 2023
Pre Tax Amount
Total other comprehensive (loss) income	$ (173,551)	$ (414,158)	$ 105,794	$ (1,193,208)
Tax Benefit (Expense)
Total other comprehensive (loss) income	44,951	96,503	(12,184)	271,086
After Tax Amount
Before reclassifications			(188,628)	(914,312)
Less: reclassification adjustments			(282,238)	7,810
Total other comprehensive (loss) income	(128,600)	(317,655)	93,610	(922,122)
Accretion of gains from terminated cash flow hedges (less than)			(46)	(9,653)
Total realized gain, net of tax	41,200		41,200		$ 41,200
Balance of gain after amortization, net of tax		400		400
Unrealized Gains and (Losses) on Cash Flow Hedges
After Tax Amount
Accretion of gains from terminated cash flow hedges (less than)			100
Unrealized losses on securities available for sale:
Pre Tax Amount
Before reclassifications	(157,750)	(337,762)	(194,259)	(1,111,187)
Less: reclassification adjustments	0	(198)	(333,170)	(2,474)
Total other comprehensive (loss) income	(157,750)	(337,564)	138,911	(1,108,713)
Tax Benefit (Expense)
Before reclassifications	40,490	76,107	52,004	249,158
Less: reclassification adjustments	0	12	74,630	714
Total other comprehensive (loss) income	40,490	76,095	(22,626)	248,444
After Tax Amount
Before reclassifications	(117,260)	(261,655)	(142,255)	(862,029)
Less: reclassification adjustments	0	(186)	(258,540)	(1,760)
Total other comprehensive (loss) income	(117,260)	(261,469)	116,285	(860,269)
Unrealized losses on cash flow hedges:
Pre Tax Amount
Before reclassifications	(29,022)	(72,667)	(66,168)	(71,182)
Less: reclassification adjustments	(13,723)	3,755	(34,557)	12,797
Total other comprehensive (loss) income	(15,299)	(76,422)	(31,611)	(83,979)
Tax Benefit (Expense)
Before reclassifications	8,193	19,304	19,795	18,899
Less: reclassification adjustments	3,874	(1,056)	9,757	(3,598)
Total other comprehensive (loss) income	4,319	20,360	10,038	22,497
After Tax Amount
Before reclassifications	(20,829)	(53,363)	(46,373)	(52,283)
Less: reclassification adjustments	(9,849)	2,699	(24,800)	9,199
Total other comprehensive (loss) income	(10,980)	(56,062)	(21,573)	(61,482)
Defined benefit pension plans:
Pre Tax Amount
Total other comprehensive (loss) income	(502)	(172)	(1,506)	(516)
Tax Benefit (Expense)
Total other comprehensive (loss) income	142	48	404	145
After Tax Amount
Before reclassifications			0	0
Less: reclassification adjustments			1,102	371
Total other comprehensive (loss) income	(360)	(124)	(1,102)	(371)
Change in actuarial net loss
Pre Tax Amount
Before reclassifications	0	0	0	0
Tax Benefit (Expense)
Before reclassifications	0	0	0	0
After Tax Amount
Before reclassifications	0	0	0	0
Less: amortization of actuarial net loss
Pre Tax Amount
Less: reclassification adjustments	(2,468)	(2,799)	(7,404)	(8,395)
Tax Benefit (Expense)
Less: reclassification adjustments	697	787	2,091	2,360
After Tax Amount
Less: reclassification adjustments	(1,771)	(2,012)	(5,313)	(6,035)
Less: accretion of prior service credit
Pre Tax Amount
Less: reclassification adjustments	2,970	2,971	8,910	8,911
Tax Benefit (Expense)
Less: reclassification adjustments	(839)	(835)	(2,495)	(2,505)
After Tax Amount
Less: reclassification adjustments	$ 2,131	$ 2,136	$ 6,415	$ 6,406