Investment Securities - Gross Unrealized Losses and Fair Value, Aggregated by Investment Category (Detail) $ in Thousands	Sep. 30, 2020 USD ($)
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	$ 167,038
Less than 12 Months, Unrealized Losses	(358)
12 Months or More, Fair Value	0
12 Months or More, Unrealized Losses	0
Fair Value, Total	167,038
Unrealized Losses	(358)
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	107,610
Less than 12 Months, Unrealized Losses	(174)
12 Months or More, Fair Value	0
12 Months or More, Unrealized Losses	0
Fair Value, Total	107,610
Unrealized Losses	(174)
Agency-guaranteed residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	19,019
Less than 12 Months, Unrealized Losses	(80)
12 Months or More, Fair Value	0
12 Months or More, Unrealized Losses	0
Fair Value, Total	19,019
Unrealized Losses	(80)
Corporate notes
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	40,409
Less than 12 Months, Unrealized Losses	(104)
12 Months or More, Fair Value	0
12 Months or More, Unrealized Losses	0
Fair Value, Total	40,409
Unrealized Losses	$ (104)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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