Investment Securities (Schedule of Available-for-Sale Investment Securities Gross Gains and Gross Losses Realized) (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Realized gains on investment securities	$ 605,000	$ 258,000
Realized losses on investment securities	(45,000)	(8,000)
Net realized gains on investment securities	560,000	250,000
Unrealized gains on equity securities with readily determinable fair value	2,290,000	180,000
Unrealized losses on equity securities with readily determinable fair value	(1,452,000)	(2,641,000)
Net unrealized gains (losses) on equity securities with readily determinable fair value	838,000	(2,461,000)
Upward adjustments of equity securities without readily determinable fair values	0	0
Downward adjustments of equity securities without readily determinable fair values	0	0
Impairment of equity securities without readily determinable fair values	0	(571,000)
Adjustment and impairment, net, of equity securities without readily determinable fair values	0	(571,000)
Gains (losses) on investment securities, net	1,398,000	(2,782,000)
Proceeds from sales of available-for-sale securities	0	0
Proceeds from sales of equity securities with readily determinable fair value	23,592,000	18,753,000
Proceeds from sales and capital distributions of equity securities without readily determinable fair value	$ 67,000	$ 250,000