Investment Securities (Narrative) (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Interest receivable	$ 37,100,000	$ 37,100,000	$ 36,900,000
Held-to-maturity debt securities	6,944,000,000	6,944,000,000	6,564,879,000
Held-to-maturity investment securities in non-accrual status	0	0	0
Investment securities available-for-sale, at fair value	7,759,341,000	7,759,341,000	$ 7,892,697,000
Equity Securities, FV-NI, Realized Loss	(48,000)	(20,500,000)
Total Loss Recognized, Portion Included In Provision For Credit Losses		3,800,000
Decrease in unrealized losses		18,500,000
Callable
Schedule of Investments [Line Items]
Held-to-maturity debt securities	900,000,000	900,000,000
Investment securities available-for-sale, at fair value	$ 2,600,000,000	$ 2,600,000,000