Pension and Other Postretirement Benefit Plans - Benefit Payments Expected to be Paid (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Retirement Plan [Member]
2021	$ 1,386
2022	1,231
2023	1,247
2024	1,228
2025	1,214
2026 - 2030	6,020
Other Postretirement Benefits Plan [Member]
2021	255
2022	299
2023	310
2024	315
2025	333
2026 - 2030	2,029
Directors' Plan [Member]
2021	288
2022	288
2023	256
2024	220
2025	192
2026 - 2030	$ 736

Amount of benefits for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following latest fiscal year.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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Amount of benefits for defined benefit plan expected to be paid in next fiscal year following latest fiscal year.

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Amount of benefits for defined benefit plan expected to be paid in fifth fiscal year following latest fiscal year.

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Amount of benefits for defined benefit plan expected to be paid in fourth fiscal year following latest fiscal year.

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Amount of benefits for defined benefit plan expected to be paid in third fiscal year following latest fiscal year.

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Amount of benefits for defined benefit plan expected to be paid in second fiscal year following latest fiscal year.

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