Investment Securities (Disclosure Regarding Length of Time on Investment Securities with Temporary Impairment) (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, fair value	$ 32,746	$ 7,627
Less than 12 months, gross unrealized losses	(1,007)	(48)
12 months or longer, fair value	406	406
12 months or longer, gross unrealized losses	(16)	(17)
Total, fair value	33,152	8,033
Total, gross unrealized losses	(1,023)	(65)
Agency Obligations
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, fair value	6,903	1,995
Less than 12 months, gross unrealized losses	(95)	(5)
12 months or longer, fair value	0	0
12 months or longer, gross unrealized losses	0	0
Total, fair value	6,903	1,995
Total, gross unrealized losses	(95)	(5)
State And Municipal Obligations
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, fair value	19,697	4,846
Less than 12 months, gross unrealized losses	(809)	(41)
12 months or longer, fair value	406	406
12 months or longer, gross unrealized losses	(16)	(17)
Total, fair value	20,103	5,252
Total, gross unrealized losses	(825)	(58)
Corporate Obligations
Schedule of Held-to-maturity Securities [Line Items]
Less than 12 months, fair value	6,146	786
Less than 12 months, gross unrealized losses	(103)	(2)
12 months or longer, fair value	0	0
12 months or longer, gross unrealized losses	0	0
Total, fair value	6,146	786
Total, gross unrealized losses	$ (103)	$ (2)