Investment Securities (Schedule of Realized Gain (Loss)) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Realized gains on investment securities	$ 801	$ 1,051	$ 1,348	$ 1,057
Realized losses on investment securities	(5)	(50)	(96)	(1,051)
Net realized gains on investment securities	796	1,001	1,252	6
Unrealized gains on equity securities with readily determinable fair value	165	530	2,299	2,632
Unrealized losses on equity securities with readily determinable fair value	(251)	(1,111)	(460)	(2,176)
Net unrealized (losses) gains on equity securities with readily determinable fair value	(86)	(581)	1,839	456
Upward adjustments of equity securities without readily determinable fair values	0	0	110	156
Downward adjustments of equity securities without readily determinable fair values	0	0		0
Impairment of equity securities without readily determinable fair values	0	(330)	(263)	(867)
Adjustment and impairment, net, of equity securities without readily determinable fair values	0	(330)	(153)	(711)
Other than temporary impairment charges	0	0	0	0
Gains (losses) on investment securities, net	710	90	2,938	(249)
Proceeds from sales of available-for-sale securities	238,008	649	905,926	209,640
Proceeds from sales of equity securities with readily determinable fair value	5,200	1,895	16,200	1,895
Proceeds from sales and capital distributions of equity securities without readily determinable fair value	$ 852	$ 64	$ 1,461	$ 680