Other Comprehensive Income - Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Unrealized losses on securities available for sale:
Change in fair value of securities available for sale, Pre Tax Amount	$ (337,762)	$ (27,741)	$ (1,111,187)	$ (90,088)
Less: reclassification adjustments for gains included in net income, Pre-Tax Amount	(198)	1	(2,474)	1,166
Net change in fair value of securities available for sale, Pre Tax Amount	(337,564)	(27,742)	(1,108,713)	(91,254)
Unrealized gains (losses) on cash flow hedges:
Change in fair value of cash flow hedges, Pre Tax Amount	(72,667)	0	(71,182)	0
Less: net cash flow hedge gains reclassified into interest income, Pre Tax Amount	3,755	7,851	12,797	24,344
Net change in fair value of cash flow hedges, Pre Tax Amount	(76,422)	(7,851)	(83,979)	(24,344)
Defined benefit pension plans:
Change in actuarial loss, Pre Tax Amount	0	0	0	0
Less: amortization of actuarial net loss, Pre Tax Amount	(2,799)	(3,537)	(8,395)	(10,612)
Less: amortization of prior service credit, pre tax amount	2,971	2,945	8,911	8,835
Net change in other comprehensive income for defined benefit postretirement plans, Pre Tax Amount	(172)	592	(516)	1,777
Total other comprehensive income, Pre Tax Amount	(414,158)	(35,001)	(1,193,208)	(113,821)
Unrealized losses on securities available for sale:
Change in fair value of securities available for sale, Tax (Expense) Benefit	76,107	6,132	249,158	19,911
Less: reclassification adjustments for gains included in net income, Tax (Expense) Benefit	12	0	714	(257)
Net change in fair value of securities available for sale, Tax (Expense) Benefit	76,095	6,132	248,444	20,168
Unrealized losses on cash flow hedges:
Change in fair value of cash flow hedges, Tax (Expense) Benefit	19,304	0	18,899	0
Less: net cash flow hedge losses reclassified into interest income, Tax (Expense) Benefit	(1,056)	(2,207)	(3,598)	(6,843)
Net change in fair value of cash flow hedges, Tax (Expense) Benefit	20,360	2,207	22,497	6,843
Defined benefit pension plans:
Change in actuarial net loss, Tax (Expense) Benefit	0	0	0	0
Less: amortization of actuarial net loss, Tax (Expense) Benefit	787	994	2,360	2,983
Less: net accretion of prior service credit, Tax (Expense) Benefit	(835)	(828)	(2,505)	(2,484)
Net change in other comprehensive income for defined benefit postretirement plans, Tax (Expense) Benefit	48	(166)	145	(499)
Total other comprehensive income, Tax (Expense) Benefit	96,503	8,173	271,086	26,512
Unrealized losses on securities available for sale:
Change in fair value of securities available for sale, After Tax Amount	(261,655)	(21,609)	(862,029)	(70,177)
Less: reclassification adjustment for gains included in net income, After Tax Amount	(186)	1	(1,760)	909
Net change in fair value of securities available for sale, After Tax Amount	(261,469)	(21,610)	(860,269)	(71,086)
Unrealized losses on cash flow hedges:
Change in fair value of cash flow hedges, After Tax Amount	(53,363)	0	(52,283)	0
Less: net cash flow hedge losses reclassified into interest income, Amount After Tax	2,699	5,644	9,199	17,501
Net change in fair value of cash flow hedges, Amount After Tax	(56,062)	(5,644)	(61,482)	(17,501)
Defined benefit pension plans:
Change in actuarial net loss, After Tax Amount	0	0	0	0
Less: amortization of actuarial net loss, After Tax Amount	(2,012)	(2,543)	(6,035)	(7,629)
Less: amortization of prior service credit, After Tax Amount	2,136	2,117	6,406	6,351
Net change in other comprehensive income for defined benefit postretirement plans, Amount After Tax	(124)	426	(371)	1,278
Total other comprehensive income, After Tax Amount	(317,655)	(26,828)	(922,122)	(87,309)
Total realized gain, net of tax	41,200	41,200	41,200	41,200
Balance of gain after amortization, net of tax	$ 400	$ 12,300	$ 400	$ 12,300