Accumulated Other Comprehensive (Loss) Income, Net of Tax (Schedule of Accumulated Other Comprehensive Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	$ (64,069)	$ (29,766)	$ (85,281)	$ (93,968)
Net of tax	(2,967)	(1,572)	(5,097)	(4,677)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net of tax	(717)	(829)	(2,248)	(2,450)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges | Reclassification out of accumualted comprehensive income
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	268	293	837	867
Net of tax	(717)	(829)	(2,248)	(2,450)
Hedge terminations	(76)	(76)	(229)	(229)
Premium amortization	(909)	(1,046)	(2,856)	(3,088)
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss)
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Actuarial loss amortization	(835)	(1,008)	(1,657)	(3,023)
Defined benefit pension and postretirement benefit plans
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net of tax	(609)	(743)	(1,208)	(2,227)
Income tax expense	226	265	449	796
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	593		593	0
Net of tax	(1,641)	0	(1,641)	0
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent | Reclassification out of accumualted comprehensive income
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net realized (losses)	$ (2,234)	0	$ (2,234)	$ 0
Income tax expense		$ 0