Investment Securities (Schedule of Realized Gain (Loss)) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Realized gains on investment securities	$ 78	$ 801	$ 725	$ 1,348
Realized losses on investment securities	(28)	(5)	(525)	(96)
Net realized gains on investment securities	50	796	200	1,252
Unrealized gains on equity securities with readily determinable fair value	471	165	2,118	2,299
Unrealized losses on equity securities with readily determinable fair value	(110)	(251)	(3,766)	(460)
Net unrealized gains (losses) on equity securities with readily determinable fair value	361	(86)	(1,648)	1,839
Upward adjustments of equity securities without readily determinable fair values	0	0	393	110
Downward adjustments of equity securities without readily determinable fair values	0	0	0	0
Impairment of equity securities without readily determinable fair values	0	0	(2,085)	(263)
Adjustment and impairment, net, of equity securities without readily determinable fair values	0	0	(1,692)	(153)
Other than temporary impairment charges	0	0	0	0
Gains (losses) on investment securities, net	411	710	(3,140)	2,938
Proceeds from sales of available-for-sale securities	0	238,008	502,676	905,926
Proceeds from sales of equity securities with readily determinable fair value	2,500	5,200	6,530	16,200
Proceeds from sales and capital distributions of equity securities without readily determinable fair value	$ 1,247	$ 852	$ 1,691	$ 1,461