Maximum granting period for stock option.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Percentage

+ References

No definition available.

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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- Definition

Unrecognized cost of unvested share-based compensation awards.

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- Definition

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.

+ References

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- Definition

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

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

The cash outflow to reacquire common stock during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
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- Definition

Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

+ References

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- Definition

The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

+ References

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- Definition

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

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- Definition

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.

+ References

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- Definition

Description of award terms as to how many shares or portion of an award are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, to sell the shares, and be entitled to the cash proceeds of such sale. For example, vesting may be expressed as being 25 percent of the shares under option on each anniversary of the grant date.

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- Definition

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).

+ References

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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

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.

+ References

No definition available.

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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- Definition

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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- Definition

Number of options outstanding, including both vested and non-vested options.

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- Definition

Amount of stock repurchase plan authorized.

+ References

No definition available.

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- Definition

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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Share Based Compensation (Details Textual) - USD ($)	3 Months Ended	12 Months Ended
Share Based Compensation (Details Textual) - USD ($)	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2018	Jan. 26, 2018	Jan. 31, 2016	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Repurchased During Period, Shares	2,400,000	1,700,000	2,700,000	2,400,000
Number of shares authorized for awards		6,800,000.0
Number of shares available for future issuance		4,100,000
Share-based compensation expense		$ 14,300,000	$ 15,800,000	$ 11,600,000
Tax benefit from share-based compensation expense		$ 5,500,000	$ 6,000,000	4,400,000
Award vesting period		3 years
Units outstanding		1,723,000	1,648,000
Proceeds from Stock Options Exercised		$ 1,600,000
Portion of an award vesting for the 2012 SAR grant		1/3 vesting after each year
Award vesting percentage		33.33%
Payments for Repurchase of Common Stock	$ 125,400,000	$ 100,000,000	$ 120,100,000	$ 125,400,000
Stock Repurchase Program, Authorized Amount					$ 250,000,000	$ 170,000,000	$ 300,000,000	$ 250,000,000
Stock Options SARs Granted Since 2004 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum granting period for stock option		7 years
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units outstanding		966,115
Stock Option SAR Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost not yet recognized		$ 7,000,000
Compensation cost not yet recognized, period for recognition		1 year 8 months
Units outstanding		756,788
Restricted Stock and Performance Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
Compensation cost not yet recognized		$ 8,400,000
Compensation cost not yet recognized, period for recognition		1 year 8 months
Fair value of restricted stock units and performance shares vested during period		$ 6,500,000	$ 7,500,000	$ 7,200,000
Phantom Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units granted during period		24,195
Units outstanding		208,163
Series A and Series B preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Shares Authorized		5,000,000
Preferred Stock, Par or Stated Value Per Share		$ 1.00