Comprehensive Income - Components of Total Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net Income	$ 95,613	$ 81,664	$ 94,836	$ 106,898	$ 177,277	$ 201,734
AFS securities - all other:
Change in net unrealized gain on AFS securities arising during the period	(149,552)		18,040		(351,786)	(27,927)
Related income tax effect	34,845		(4,203)		81,966	6,507
Net reclassification adjustment for gains included in net income	0		0		0	(1,444)
Related income tax expense	0		0		0	336
Net effect of AFS securities on other comprehensive income	(114,707)		13,837		(269,820)	(22,528)
Cash flow hedge derivatives:
Unrealized gain on cash flow hedge before reclassification to interest expense	11,216		(8,243)		33,910	11,074
Related income tax effect	(2,613)		1,921		(7,901)	(2,580)
Net reclassification adjustment for losses included in net income	(263)		363		79	586
Related income tax effect	62		(85)		(18)	(137)
Net effect of cash flow hedge derivatives on other comprehensive income	8,402		(6,044)		26,070	8,943
Pension plan:
Recognized net actuarial loss	832		1,589		1,656	3,161
Related income tax benefit	(192)		(720)		(375)	(1,423)
Net effect of change in defined benefit pension plan on other comprehensive income	640		869		1,281	1,738
Net current-period other comprehensive income, net of tax	(105,665)	(136,804)	8,662	(20,509)	(242,469)	(11,847)
Total Comprehensive (Loss) Income	$ (10,052)	$ (55,140)	$ 103,498	$ 86,389	$ (65,192)	$ 189,887