Share-based compensation plans - Stock Activity - RSU, PSU, DSU (Details) - $ / shares	6 Months Ended	12 Months Ended
Jun. 30, 2025	Dec. 31, 2024
Restricted Stock Units
Shares (in thousands)
Nonvested, beginning balance, shares	290,400
Granted, shares	145,800
Forfeited or expired, shares	(19,800)
Vested, shares	(134,900)
Nonvested, ending balance, shares	281,500	290,400
Weighted-Average Grant Date Fair Value Per Share
Nonvested, beginning balance (dollars per share)	$ 74.24
Granted (dollars per share)	86.71
Forfeited or expired (dollars per share)	83.53
Vested (dollars per share)	69.49
Nonvested, ending balance (dollars per share)	$ 82.32	$ 74.24
Performance Shares Units
Shares (in thousands)
Nonvested, beginning balance, shares	639,100
Granted, shares	221,700
Forfeited or expired, shares	(54,100)
Vested, shares	(235,000.0)
Nonvested, ending balance, shares	571,700	639,100
Weighted-Average Grant Date Fair Value Per Share
Nonvested, beginning balance (dollars per share)	$ 72.64
Granted (dollars per share)	89.86
Forfeited or expired (dollars per share)	80.66
Vested (dollars per share)	67.17
Nonvested, ending balance (dollars per share)	$ 80.81	$ 72.64
Actual shares earned and distributed (shares)		440,200
Target shares (shares)		235,000.0
Deferred Stock Units
Shares (in thousands)
Nonvested, beginning balance, shares	13,600
Granted, shares	14,800
Vested, shares	(13,600)
Nonvested, ending balance, shares	14,800	13,600
Weighted-Average Grant Date Fair Value Per Share
Nonvested, beginning balance (dollars per share)	$ 87.93
Granted (dollars per share)	92.19
Vested (dollars per share)	87.93
Nonvested, ending balance (dollars per share)	$ 92.19	$ 87.93

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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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).

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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

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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- Definition

Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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- Definition

Number of shares authorized for issuance under share-based payment arrangement.

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-Topic 718
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-Section 50
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-Publisher FASB
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Number of shares issued under share-based payment arrangement.

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