Comprehensive Income - Components of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 4,487,050	$ 4,595,140	$ 4,718,628	$ 4,393,713	$ 4,332,698	$ 4,297,620	$ 4,718,628	$ 4,297,620
Net current-period other comprehensive income, net of tax	(104,947)	(105,665)	(136,804)	(11,762)	8,662	(20,509)	(347,416)	(23,609)
Ending Balance	4,440,086	4,487,050	4,595,140	4,430,766	4,393,713	4,332,698	4,440,086	4,430,766
Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(29,841)				(29,841)
Other comprehensive income before reclassification							0
Amounts reclassified from accumulated other comprehensive income							1,997
Net current-period other comprehensive income, net of tax							1,997
Ending Balance	(27,844)						(27,844)
Unrealized Gains/Losses on AFS Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			8,594				8,594
Other comprehensive income before reclassification							(387,768)
Amounts reclassified from accumulated other comprehensive income							(2)
Net current-period other comprehensive income, net of tax							(387,770)
Ending Balance	(379,176)						(379,176)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(247,357)	(141,692)	(4,888)	10,523	1,861	22,370	(4,888)	22,370
Other comprehensive income before reclassification							(347,614)
Amounts reclassified from accumulated other comprehensive income							198
Net current-period other comprehensive income, net of tax	(104,947)	(105,665)	(136,804)	(11,762)	8,662	(20,509)	(347,416)
Ending Balance	(352,304)	$ (247,357)	(141,692)	$ (1,239)	$ 10,523	$ 1,861	(352,304)	$ (1,239)
Unrealized Gains/Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 16,359				16,359
Other comprehensive income before reclassification							40,154
Amounts reclassified from accumulated other comprehensive income							(1,797)
Net current-period other comprehensive income, net of tax							38,357
Ending Balance	$ 54,716						$ 54,716