Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Unrealized gains (losses) arising during the period on available for sale securities, tax	$ 131	$ 1,223	$ (259)
Reclassification adjustment for net gain on sales of available for sale securities included in net income, tax	(98)	(394)	(29)
Change in defined benefit plans, tax	(134)	(79)	363
Reclassification adjustment for settlement gains and activity related to benefit plans, tax	$ (6)	$ (26)	$ (156)
Income tax impacts of the components of other comprehensive income	21.00%	21.00%	21.00%

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount, before reclassification adjustment, of tax (expense) benefit for (increase) decrease in accumulated other comprehensive income for defined benefit plan.

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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan.

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Amount, before adjustment, of tax expense (benefit) for unrealized holding gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Excludes tax expense (benefit) for unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale.

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