Investment Securities - Amount of Securities in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than twelve months, fair value	$ 14,360	$ 0
Debt securities, held-to-maturity, continuous unrealized loss position, less than 12 months, accumulated loss	(372)	0
Twelve months or longer, fair value	0	0
Debt securities, held-to-maturity, continuous unrealized loss position, 12 months or longer, accumulated loss	0	0
Total, fair value	14,360	0
Debt securities, held-to-maturity, unrealized loss position, accumulated loss	(372)	0
Debt Securities, Available-for-sale, Unrealized Gain (Loss) [Abstract]
Less than twelve months, fair value	135,115	18,222
Available-for-sale securities, continuous unrealized loss position, less than 12 months, accumulated loss	(1,879)	(77)
Twelve months or longer, fair value	3,124	31
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, accumulated loss	(135)	(1)
Total, fair value	138,239	18,253
Available-for-sale securities, continuous unrealized loss position, accumulated loss	(2,014)	(78)
Residential Mortgage-Backed Securities [Member]
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than twelve months, fair value	14,360
Debt securities, held-to-maturity, continuous unrealized loss position, less than 12 months, accumulated loss	(372)
Twelve months or longer, fair value	0
Debt securities, held-to-maturity, continuous unrealized loss position, 12 months or longer, accumulated loss	0
Total, fair value	14,360
Debt securities, held-to-maturity, unrealized loss position, accumulated loss	(372)
Debt Securities, Available-for-sale, Unrealized Gain (Loss) [Abstract]
Less than twelve months, fair value	133,703	13,677
Available-for-sale securities, continuous unrealized loss position, less than 12 months, accumulated loss	(1,878)	(62)
Twelve months or longer, fair value	3,124	31
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, accumulated loss	(135)	(1)
Total, fair value	136,827	13,708
Available-for-sale securities, continuous unrealized loss position, accumulated loss	(2,013)	(63)
Collateralized Mortgage Obligations [Member]
Debt Securities, Available-for-sale, Unrealized Gain (Loss) [Abstract]
Less than twelve months, fair value		4,545
Available-for-sale securities, continuous unrealized loss position, less than 12 months, accumulated loss		(15)
Twelve months or longer, fair value		0
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, accumulated loss		0
Total, fair value		4,545
Available-for-sale securities, continuous unrealized loss position, accumulated loss		$ (15)
Corporate Bonds [Member]
Debt Securities, Available-for-sale, Unrealized Gain (Loss) [Abstract]
Less than twelve months, fair value	1,412
Available-for-sale securities, continuous unrealized loss position, less than 12 months, accumulated loss	(1)
Twelve months or longer, fair value	0
Available-for-sale securities, continuous unrealized loss position, 12 months or longer, accumulated loss	0
Total, fair value	1,412
Available-for-sale securities, continuous unrealized loss position, accumulated loss	$ (1)

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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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