Share Transactions - Share-based compensation (Details) - $ / shares	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants during period, options (shares)	1,218,465	1,116,073
Weighted average grant date fair value, options (per share)	$ 9.20	$ 8.14
Performance shares and units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants during period, other than options (shares)	685,104	557,204
Weighted average grant date fair value, other than options (per share)	$ 37.38	$ 44.17
Restricted shares and units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants during period, other than options (shares)	1,168,577	910,879
Weighted average grant date fair value, other than options (per share)	$ 35.82	$ 42.36

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- 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.

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- Definition

Gross number of share options (or share units) granted during the period.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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