Securities - Schedule of Components of Investment Securities Gains, Net (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Available-for-sale debt securities:
Gains realized on sales	$ 7,255	$ 4,636	$ 581
Losses realized on sales	(274)	(1,418)	(3)
Equity securities with readily determinable fair values:
Fair value adjustments, net	110,768
Equity securities without readily determinable fair values:
Fair value adjustments, net	2,885	(973)	2,943
Total investment securities gains, net	$ 120,634	$ 2,245	$ 3,521

Equity securities with out readily determinable fair values adjustments net.

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Amount of unrealized and realized gain (loss) on investment in debt and equity securities.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
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Amount of realized gain on 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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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Amount of realized loss on 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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