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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.

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Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
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-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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- Definition

Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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Retirement benefits - Asset Allocation Target and Actual Percentage (Details)	Dec. 31, 2019	Dec. 31, 2018
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	100.00%	100.00%
Asset category, Target
Target	100.00%
Pension benefits \| Equity securities
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	71.00%	69.00%
Asset category, Target
Target	70.00%
Pension benefits \| Equity securities \| Minimum
Asset category, Target
Target	65.00%
Pension benefits \| Equity securities \| Maximum
Asset category, Target
Target	75.00%
Pension benefits \| Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	29.00%	31.00%
Asset category, Target
Target	30.00%
Pension benefits \| Fixed income securities \| Minimum
Asset category, Target
Target	25.00%
Pension benefits \| Fixed income securities \| Maximum
Asset category, Target
Target	35.00%
Other benefits
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	100.00%	100.00%
Asset category, Target
Target	100.00%
Other benefits \| Equity securities
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	71.00%	70.00%
Asset category, Target
Target	70.00%
Other benefits \| Equity securities \| Minimum
Asset category, Target
Target	65.00%
Other benefits \| Equity securities \| Maximum
Asset category, Target
Target	75.00%
Other benefits \| Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Actual asset allocation	29.00%	30.00%
Asset category, Target
Target	30.00%
Other benefits \| Fixed income securities \| Minimum
Asset category, Target
Target	25.00%
Other benefits \| Fixed income securities \| Maximum
Asset category, Target
Target	35.00%