Consolidated Statements of Income and Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Reclassification adjustment for net realized (gains) losses included in income	$ 141	$ 80	$ (666)	$ (41)
Reclassification adjustment for employee benefit costs included in expense	1,645	1,072	3,312	2,144
Reclassifications for federal income tax expense (benefit)	$ (316)	$ (207)	$ (835)	$ (458)

Amount, before tax, of reclassification adjustment from accumulated other comprehensive (income) loss for net period benefit cost (credit) of defined benefit plan.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=124509347&loc=d3e637-108580

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=124509347&loc=d3e689-108580

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 17A
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL34724391-108580

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