Investment Securities (Schedule of Realized Gain (Loss)) (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Realized gains on investment securities	$ 216	$ 496
Realized losses on investment securities	(6)	(5)
Net realized gains on investment securities	210	491
Unrealized gains on equity securities with readily determinable fair value	1,875	0
Unrealized losses on equity securities with readily determinable fair value	(901)	(3,546)
Net unrealized gains (losses) on equity securities with readily determinable fair value	974	(3,546)
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)
Adjustment and impairment, net, of equity securities without readily determinable fair values	(30)	(1,304)
Gains (losses) on investment securities, net	1,154	(4,359)
Proceeds from sales of available-for-sale securities	0	0
Proceeds from sales of equity securities with readily determinable fair value	1,509	30
Proceeds from sales and capital distributions of equity securities without readily determinable fair value	$ 386	$ 288

Amount of unrealized gain on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
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Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of unrealized loss on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of impairment loss on investment in equity security without readily determinable fair value.

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Amount of gain from upward price adjustment on investment in equity security without readily determinable fair value.

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Amount of unrealized and realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI).

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Amount of realized gain (loss) on investment in marketable security, excluding other-than-temporary impairment (OTTI).

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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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The cash inflow associated with the sale of securities classified as trading securities and held for investment purposes. Excludes proceeds from trading securities purchased and held principally for the purpose of selling them in the near term (thus held for only a short period of time).

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Gross realized gains on marketable securities.

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Gross losses on marketable securities

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Proceeds from Sales and Capital Distributions of Equity Securities Without Readily Determinable Fair Value

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Securities Owned Not Readily Marketable, Period Increase (Decrease)

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