Securities - Narrative (Detail) - USD ($)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Debt Securities [Abstract]
Gross realized gains from sales of available for sale securities	$ 1,200,000	$ 100,000
Gross realized losses from sales of available for sale securities	0	0
Other-than-temporary impairment was recorded	$ 0	$ 0

The amount by which the fair value of an investment in debt and equity securities categorized as Available-for-sale is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration