Share-based compensation (Rollforward Of Company's Restricted Stock) (Details) - $ / shares	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Restricted stock
Number of Restricted Stock [Roll Forward]
Number of unvested restricted stock, beginning of period	2,853,870	3,051,811	3,263,295
Number of restricted stock, granted	1,166,706	1,193,016	1,288,042
Number of restricted stock, vested and issued	(1,142,911)	(1,191,452)	(1,283,185)
Number of restricted stock, forfeited	(203,850)	(199,505)	(216,341)
Number of unvested restricted stock, end of period	2,673,815	2,853,870	3,051,811
Weighted-Average Grant-Day Fair Value [Roll Forward]
Weighted average grant-day fair value of unvested restricted stock outstanding, beginning of period (US$ per share)	$ 172.39	$ 152.19	$ 142.32
Weighted average grant-day fair value of restricted stock, granted (US$ per share)	208.07	199.18	165.32
Weighted average grant-day fair value of restricted stock, vested and issued (US$ per share)	161.88	148.18	140.62
Weighted average grant-day fair value of restricted stock, forfeited (US$ per share)	186.58	168.12	150.19
Weighted average grant-day fair value of unvested restricted stock outstanding, end of period (US$ per share)	$ 191.35	$ 172.39	$ 152.19
Performance Shares
Number of Restricted Stock [Roll Forward]
Number of unvested restricted stock, beginning of period	794,792	697,191	572,318
Number of restricted stock, granted	407,825	296,944	294,315
Number of restricted stock, vested and issued	(203,533)	(199,343)	(169,442)
Number of restricted stock, forfeited	0	0	0
Number of unvested restricted stock, end of period	999,084	794,792	697,191
Weighted-Average Grant-Day Fair Value [Roll Forward]
Weighted average grant-day fair value of unvested restricted stock outstanding, beginning of period (US$ per share)	$ 173.83	$ 151.74	$ 142.38
Weighted average grant-day fair value of restricted stock, granted (US$ per share)	208.60	199.09	164.75
Weighted average grant-day fair value of restricted stock, vested and issued (US$ per share)	150.11	133.90	143.07
Weighted average grant-day fair value of restricted stock, forfeited (US$ per share)	0	0	0
Weighted average grant-day fair value of unvested restricted stock outstanding, end of period (US$ per share)	$ 192.85	$ 173.83	$ 151.74

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

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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

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-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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- 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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