Investment Securities (Narrative) (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($) security	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) security	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Investments, Debt and Equity Securities [Abstract]
Equity securities without readily determinable fair value	$ 43,900,000		$ 43,900,000
Upward adjustments of equity securities without readily determinable fair values	0	$ 0	0	$ 0
Downward adjustments of equity securities without readily determinable fair values	0	0	0	0
Impairment of equity securities without readily determinable fair values	5,000	2,148,000	4,362,000	2,178,000
Pledged securities	$ 2,500,000,000	$ 2,500,000,000	$ 2,500,000,000	$ 2,500,000,000	$ 2,600,000,000
Number of securities by a single non-government sponsored issuer exceeding 10% of shareholders' equity | security	0		0