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

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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, Number Of Plans

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Share-based Compensation Arrangement by Share-based Payment Award, Options, Assumed in Period, Weighted Average Grant Date Fair Value

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

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Shares to be issued for settlement.

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Aggregate number of common shares reserved for future issuance.

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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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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The weighted average of per share prices paid for shares purchased on the open market for issuance to employees under the plan.

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Intrinsic value of equity-based compensation awards outstanding. Excludes stock 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	May 01, 2017 USD ($) $ / shares	Aug. 11, 2014 shares	Dec. 31, 2018 USD ($) item $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
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 vesting period					5 years
Award term					10 years
Remaining shares authorized for grant \| shares					2,478,321	3,402,481
Weighted average share price of options exercised \| $ / shares					$ 35.08	$ 30.81	$ 31.18
Weighted average grant date fair value of options granted \| $ / shares					$ 7.69	$ 7.22	$ 4.72
Unrecognized compensation costs					$ 4,702,000
Unrecognized compensation costs, period for recognition					1 year 10 months 24 days
Proceeds from exercise of employee stock options					$ 28,524,000	$ 9,936,000	$ 24,338,000
Actual tax benefit realized from option exercise					$ 2,793,000	1,017,000	1,464,000
Performance Share Unit Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period					3 years
Market value of shares vested and released					$ 410,000	6,521,000	$ 4,463,000
Share unit liability, fair value attributable to past service		$ 6,701,000
Modified Performance Vesting Conditions, Weighted Average Fair Value \| $ / shares		$ 31.35
Modified Performance Vesting Conditions, Incremental Compensation Recognized		$ 1,400,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of plans \| item					3
Stock Options Assumed [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average share price of options assumed \| $ / shares					$ 16.93
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]
Modified Performance Vesting Conditions, Weighted Average Fair Value \| $ / shares			$ 24.47
Modified Performance Vesting Conditions, Incremental Compensation Recognized			$ 1,803,000
Performance Share Units [Member] \| Senior Executive and Employee Performance Share Unit Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Shares \| shares				102,375
Unrecognized compensation costs					$ 7,874,000
Unrecognized compensation costs, period for recognition					1 year 8 months 12 days
Shares to be issued for settlement.			150,000
Performance Share Units [Member] \| Senior Executive and Employee Performance Share Unit Plans [Member] \| Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period					2 years
Performance Share Units [Member] \| Senior Executive and Employee Performance Share Unit Plans [Member] \| Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period					3 years
Performance Share Units [Member] \| Senior Executive and Employee Performance Share Unit Plans [Member] \| Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period					4 years
Performance Share Units [Member] \| Senior Executive and Employee Performance Share Unit Plans [Member] \| Tranche Four [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period					5 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
Performance Shares, Liability Classified [Member] \| Senior Executive and Employee Performance Share Unit Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share unit liability			$ 1,421,000
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					$ 3,994,000
Unrecognized compensation costs, period for recognition					2 years
Deferred 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					$ 0
Share unit liability					$ 3,714,000	$ 2,645,000