Investment Securities (Narrative) (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) security	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Investments, Debt and Equity Securities [Abstract]
Equity securities without readily determinable fair value	$ 33,300
Upward adjustments of equity securities without readily determinable fair values	0	$ 393
Downward adjustments of equity securities without readily determinable fair values	0	0
Impairment of equity securities without readily determinable fair values	30	1,697
Pledged securities	$ 2,100,000	$ 1,500,000	$ 2,400,000
Number of securities by a single non-government sponsored issuer exceeding 10% of shareholders' equity | security	0