Accumulated Other Comprehensive (Loss) Income, Net of Tax (Schedule of Other 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
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 7,997,788	$ 3,329,705	$ 3,438,325	$ 3,234,625
Other comprehensive (loss) before reclassifications	(258,536)	(5,954)	(719,418)	(45,425)
Amounts reclassified from accumulated other comprehensive (loss)	2,967	1,572	5,097	4,677
Other comprehensive (loss) income, net of tax	(255,569)	(4,382)	(714,321)	(40,748)
Ending Balance	7,826,410	3,386,189	7,826,410	3,386,189
Available For Sale and Transferred Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(445,616)	35,598	4,536	67,424
Other comprehensive (loss) before reclassifications	(243,872)	(3,394)	(694,024)	(35,220)
Amounts reclassified from accumulated other comprehensive (loss)	1,641	0	1,641	0
Other comprehensive (loss) income, net of tax	(242,231)	(3,394)	(692,383)	(35,220)
Ending Balance	(687,847)	32,204	(687,847)	32,204
Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(2,082)	13,894	6,070	19,918
Other comprehensive (loss) before reclassifications	(14,416)	(2,560)	(24,099)	(10,205)
Amounts reclassified from accumulated other comprehensive (loss)	717	829	2,248	2,450
Other comprehensive (loss) income, net of tax	(13,699)	(1,731)	(21,851)	(7,755)
Ending Balance	(15,781)	12,163	(15,781)	12,163
Defined Benefit Pension and Other Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(33,634)	(43,602)	(33,186)	(45,086)
Other comprehensive (loss) before reclassifications	(248)	0	(1,295)	0
Amounts reclassified from accumulated other comprehensive (loss)	609	743	1,208	2,227
Other comprehensive (loss) income, net of tax	361	743	(87)	2,227
Ending Balance	(33,273)	(42,859)	(33,273)	(42,859)
Accumulated Other Comprehensive Income (Loss), Net of Tax
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(481,332)	5,890	(22,580)	42,256
Other comprehensive (loss) income, net of tax	(255,569)	(4,382)	(714,321)	(40,748)
Ending Balance	$ (736,901)	$ 1,508	$ (736,901)	$ 1,508