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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Amount of other expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses associated with a discontinued operation or an asset retirement obligation.

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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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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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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 highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

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The highest quantity of shares an employee can purchase under the plan per period.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Purchase price of common stock expressed as a percentage of its fair value.

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No definition available.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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Deferred Compensation Arrangement with Individual, Number of Plans

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Deferred Compensation Arrangement with Individual, Share Equivalents Balance

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Conversion unit of deferred stock units

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Deferred Stock Units Payable in Cash

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Reduction in number of shares available for grant for each award granted.

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Share-based Compensation Arrangement by Share-based Payment Award, Actual Payout, Percentage

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Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate, Amount

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Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares per Employee per Year

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Share-based compensation expense related to executive retirements. Includes new LTIP award (stock option & PVS), as well as incremental compensation cost related to award modifications and accelerated compensation costs.

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Stock-Based Compensation (Textuals) (Details)	12 Months Ended
Stock-Based Compensation (Textuals) (Details)	Dec. 31, 2017 USD ($) plan $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other charges \| $	$ 0	$ 200,000	$ 0
Share-based Compensation, Executive Retirements \| $			$ 10,400,000
Shares available for grant/issuance	4,597,102
Unrecognized compensation expense for all nonvested awards \| $	$ 17,200,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 7 months
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards, expiration period	10 years
Number of shares reduced for each award granted	1
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Awards, expiration period	10 years
Award Types Other than Stock Options and Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares reduced for each award granted	2.5
Performance-Vesting Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	92,045	115,035	147,908
Granted at target level \| $ / shares	$ 84.01	$ 60.47	$ 55.49
Employee Stock Purchase Plan (ESPP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant/issuance	4,000,000
Percentage of current market price for sales to eligible employees	85.00%
Limitation on payroll deductions of employee's base salary, percent	25.00%
Limitation on payroll deductions of employee's base salary, amount \| $	$ 25,000
Maximum number of shares per employee	2,000
Maximum number of shares per employee, per year	8,000
Purchases of shares	56,218	60,839	61,757
Annual Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	1,800	2,400	1,500
Vesting period	4 years
Granted at target level \| $ / shares	$ 86.93	$ 59.64	$ 51.53
Performance-Vesting Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	598	419	1,386
Granted at target level \| $ / shares	$ 83.47	$ 59.64	$ 54.14
Minimum [Member] \| Performance-Vesting Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual payout range	0.00%
Minimum [Member] \| Performance-Vesting Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual payout range	0.00%
Maximum [Member] \| Performance-Vesting Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual payout range	200.00%
Maximum [Member] \| Performance-Vesting Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual payout range	200.00%
Deferred Compensation Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred Compensation Arrangement with Individual, Conversion Unit	1
Number of deferred compensation plans \| plan	2
Number of deferred stock units	402,155
Number of deferred stock units payable in cash	24,296
Deferred Compensation Plans [Member] \| Non-Employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	17,284
Granted at target level \| $ / shares	$ 94.68