Condensed Consolidated Statements of Comprehensive Income (unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 11,565,000	$ 11,670,000	$ 31,701,000	$ 35,967,000
Other Comprehensive Income
Unrealized gains (losses) on available-for-sale securities, net of taxes of $21 and ($909) for three months ended September 30, 2020 and 2019, respectively and ($3,778) and ($6,562) for nine months ended September 30, 2020 and 2019, respectively.	(52,000)	2,221,000	9,250,000	16,062,000
Amortized holding losses on held-to-maturity securities transferred from available-for- sale, net of taxes of ($3) and ($8) for three months ended September 30, 2020 and 2019, respectively and ($13) and ($25) for nine months ended September 30, 2020 and 2019, respectively.	8,000	21,000	32,000	62,000
Less: reclassification adjustment for realized gains included in net income, net of taxes of $28 and $15 for three months ended September 30, 2020 and 2019, respectively and $265 and $94 for nine months ended September 30, 2020 and 2019, respectively.	(67,000)	(36,000)	(648,000)	(229,000)
Other comprehensive income, net of taxes	(111,000)	2,206,000	8,634,000	15,895,000
Comprehensive income	$ 11,454,000	$ 13,876,000	$ 40,335,000	$ 51,862,000