Pension Benefits - Assumptions Used (Details)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits
Discount rate to determine benefit obligations	2.20%	3.00%
Discount rate	3.00%	4.05%	3.45%
Expected return on plan assets	6.50%	7.25%	7.25%
Corridor	10.00%	10.00%	10.00%
Average future life expectancy (in years)	25 years 8 months 12 days	26 years 10 months 13 days	27 years 9 months 7 days

Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Average Life Expectancy

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- Definition

Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Corridor

+ References

No definition available.

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- References

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- Definition

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

+ References

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- Definition

Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan.

+ References

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- Definition

Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(3)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2919-114920

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