Maximum granting period for stock option.

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- Definition

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

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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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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- Definition

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

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- Definition

The cash outflow to reacquire common stock during the period.

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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.

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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.

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- Definition

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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Description of service or performance condition required to be met for earning right to award under share-based payment arrangement. Includes, but is not limited to, combination of market, performance or service condition.

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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).

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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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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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No definition available.

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- Definition

Number of shares authorized for issuance under share-based payment arrangement.

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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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- Definition

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

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- Definition

Amount of stock repurchase plan authorized.

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No definition available.

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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.

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Share Based Compensation (Details Textual) - USD ($)	12 Months Ended
Share Based Compensation (Details Textual) - USD ($)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 25, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Repurchased During Period, Shares	0	2,000,000.0	1,500,000
Number of shares authorized for awards	6,200,000
Number of shares available for future issuance	2,900,000
Share-based compensation expense	$ 15,900,000	$ 19,300,000	$ 19,300,000
Tax benefit from share-based compensation expense	$ 4,000,000.0	$ 4,800,000	4,800,000
Award vesting period	3 years
Units outstanding	1,467,000	1,551,000
Proceeds from Stock Options Exercised	$ 6,600,000	$ 4,400,000	3,700,000
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	$ 0	$ 150,000,000.0	$ 115,500,000
Stock Repurchase Program, Authorized Amount				$ 300,000,000
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	153,366
Stock Option SAR Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost not yet recognized	$ 6,700,000
Compensation cost not yet recognized, period for recognition	1 year 8 months 12 days
Units outstanding	1,313,577
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	$ 8,300,000
Compensation cost not yet recognized, period for recognition	1 year 9 months 18 days
Fair value of restricted stock units and performance shares vested during period	$ 10,200,000	$ 12,600,000	$ 12,000,000.0
Phantom Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units granted during period	26,552
Units outstanding	228,105
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