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Retirement Benefits Plans (Narrative) (Details) - USD ($) $ in Millions		12 Months Ended
	Jan. 01, 2011	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Company's pretax income and the aggregate compensation levels of participating employees		$ 6.6	$ 6.8	$ 6.5
Postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Years of service, less than	10 years
Health care cost trend assumption increased health care cost trend rates (as a percent)		6.25%	6.25%
Health care cost trend assumption increased health care cost trend rates (as a percent)		5.00%

X

- Definition

Defined benefit plan assumptions used calculating benefit obligation health care cost trend rate.

+ References

No definition available.

+ Details

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X

- Definition

Defined Benefit Plan, Years of Service

+ References

No definition available.

+ Details

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X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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X

- Definition

Ultimate trend rate for health care cost for defined benefit postretirement 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 (l)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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X

- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

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- Details

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