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Employee Stock Purchase Plan, Maximum Annual Contributions Per Employee, Percent

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The number of specified trading days for weighted average price of the Company's common shares listed on the New York Stock Exchange to estimate the fair values on grant date and at each reporting date.

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Modified Performance Vesting Conditions, Incremental Compensation Recognized

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Modified Performance Vesting Conditions, Weighted Average Fair Value

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grant Date Fair Value

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash. Additionally, share-based awards which were paid or settled.

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Share Based Compensation Arrangement By Share Based Payment Award, Fair Value Assumptions, Expected Volatility Rate Of Comparable Companies

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- Definition

Share Based Compensation Arrangement By Share Based Payment Award, Number Of Plans

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Share-based Compensation Arrangement by Share-based Payment Award, Term of Award

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Aggregate number of common shares reserved for future issuance.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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Amount of cash inflow from exercise of option under share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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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.

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

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Per share weighted-average price paid for shares purchased on open market for issuance under share-based payment arrangement.

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- Definition

An excess of the fair value of the modified award over the fair value of the award immediately before the modification.

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Intrinsic value of outstanding award under share-based payment arrangement. Excludes share and unit options.

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Share-based payments (Narrative) (Details)			12 Months Ended
Share-based payments (Narrative) (Details)	Sep. 11, 2018 USD ($) $ / shares	Mar. 01, 2018 USD ($) $ / shares	Dec. 31, 2020 USD ($) D item $ / shares shares	Dec. 31, 2019 USD ($) D $ / shares shares	Dec. 31, 2018 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs, period for recognition			2 years
Maximum employee contribution, percentage			4.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employer matching contribution, percentage			50.00%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employer matching contribution, percentage			100.00%
Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award term			10 years
Remaining shares authorized for grant \| shares			6,442,360	7,222,978
Weighted average share price of options exercised \| $ / shares				$ 40.32	$ 35.08
Weighted average grant date fair value of options granted \| $ / shares			$ 8.69	$ 7.52	$ 7.69
Unrecognized compensation costs			$ 4,424,000
Unrecognized compensation costs, period for recognition			2 years 2 months 12 days
Proceeds from exercise of employee stock options			$ 44,128,000	$ 41,094,000	$ 28,524,000
Actual tax benefit realized from option exercise			4,594,000	1,679,000	2,793,000
Performance Share Unit Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Market value of shares vested and released			$ 0	$ 774,000	$ 410,000
Share unit liability, fair value attributable to past service		$ 6,701,000
Incremental compensation		$ 0
Modified performance vesting conditions, weighted average fair value \| $ / shares		$ 31.35
Modified performance vesting conditions, incremental compensation recognized		$ 1,400,000
Award vesting period			3 years
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average share price of options exercised \| $ / shares			$ 51.92
Number of plans \| item			3
Performance Share Units, Equity Classified Awards [Member] \| Senior Executive and Employee Performance Share Unit Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average expected volatility of comparable companies					34.10%
Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of trading days of volume weighted average price for fair value estimation \| D			20	20
Performance Share Units [Member] \| Senior Executive and Employee Performance Share Unit Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs			$ 10,447,000
Unrecognized compensation costs, period for recognition			2 years
Performance Share Units [Member] \| Sign-on Grant Performance Share Unit Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Modified performance vesting conditions, weighted average fair value \| $ / shares	$ 43.34
Modified performance vesting conditions, incremental compensation recognized	$ 838,000
Restricted Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of trading days of volume weighted average price for fair value estimation \| D			20
Restricted Share Units [Member] \| Senior Executive and Employee Performance Share Unit Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs			$ 1,980,000
Unrecognized compensation costs, period for recognition			1 year 8 months 12 days
Deferred Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of trading days of volume weighted average price for fair value estimation \| D			20
Deferred Share Units [Member] \| Senior Executive and Employee Performance Share Unit Plans [Member] \| Current Liabilities [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share unit liability			$ 9,597,000	$ 5,130,000