Comprehensive Income - Accumulated Other Comprehensive Income (Loss), Net (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 17,876,020	$ 16,446,508	$ 17,903,405	$ 16,187,283
Net gain (loss) during period	(129,105)	(38,496)	(378,912)	(113,942)
Ending balance	25,794,531	16,720,304	25,794,531	16,720,304
Investment Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			77,625
Net gain (loss) during period			(206,918)
Ending balance	(129,293)		(129,293)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(267,145)
Net gain (loss) during period			6,167
Ending balance	(260,978)		(260,978)
Accumulated Other Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			61,942
Net gain (loss) during period			(178,161)
Ending balance	(116,219)		(116,219)
Accumulated Other Comprehensive Income (Loss), Net [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(377,385)	(138,478)	(127,578)	(63,032)
Net gain (loss) during period			(378,912)
Ending balance	$ (506,490)	$ (176,974)	$ (506,490)	$ (176,974)