Weighted Average Number of Shares Diluted (Details) - shares shares in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings per share [abstract]
Weighted average number of shares (basic) (in shares)	129.1	131.0	139.4
Dilutive effect of outstanding awards under SBC plans (in shares)	0.0	0.8	1.2
Weighted average number of shares (diluted) (in shares)	129.1	131.8	140.6
Stock-based awards excluded from diluted weighted average per share calculation (in shares)	0.3	0.3	0.3

Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount1

No definition available.

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- Definition

The weighted average number of ordinary shares outstanding plus the weighted average number of ordinary shares that would be issued on the conversion of all the dilutive potential ordinary shares into ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Number 33
-IssueDate 2020-01-01
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-URIDate 2020-01-01

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- Definition

The number of dilutive potential ordinary shares that relate to the assumed exercise of the entity's share options.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 33
-IssueDate 2020-01-01
-Paragraph 70
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-URIDate 2020-01-01

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- References

No definition available.

+ Details

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- Definition

The number of ordinary shares outstanding at the beginning of the period, adjusted by the number of ordinary shares bought back or issued during the period multiplied by a time-weighting factor.

+ References

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