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Percentage of share-based compensation awards earned for the reporting period.

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Represents the aggregate grant date fair value of equity-based awards granted during the period.

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Number of share options and Stock Appreciation Rights (SARS) exercised during the current period.

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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.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The amount of expense, net of income tax, 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.

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Face amount or stated value per share of common stock.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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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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 estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Number of additional shares authorized for issuance under an established share-based compensation plan.

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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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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Value, before forfeitures, of stock or other type of equity granted of any equity-based compensation plan other than an employee stock ownership plan (ESOP).

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Stock Compensation Plans - Omnibus Plan (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2004	Aug. 31, 2014
Stock Compensation Plans
Par value of shares of common stock (in dollars per share)	$ 0.01	$ 0.01
Stock-based compensation expense and related income tax benefits
Stock-based compensation expense	$ 5.8	$ 6.5	$ 6.0
Income tax benefit	(2.2)	(2.5)	(2.3)
Stock-based compensation, net of income tax benefit	3.6	4.0	3.7
Compensation costs related to equity awards and amounts recognized
Compensation expense recognized	$ (5.8)	$ (6.5)	$ (6.0)
Stock options awarded
Nonqualified stock options granted (in shares)	113,935
Per share weighted-average exercise price (in dollars per share)	$ 58.03
Per share weighted-average grant date fair value (in dollars per share)	$ 13.51
Number of Stock Options
Options outstanding at the beginning of the period (in shares)	526,611
Add: Options granted (in shares)	113,935
Less: Options exercised (in shares)	105,806
Less: Options forfeited/cancelled (in shares)	4,278
Options outstanding at the end of the period (in shares)	530,462	526,611
Weighted-Average Exercise Price
Options outstanding at the beginning of the period (in dollars per share)	$ 31.94
Add: Options granted (in dollars per share)	58.03
Less: Options exercised (in dollars per share)	27.29
Less: Options forfeited/cancelled (in dollars per share)	46.89
Options outstanding at the end of the period (in dollars per share)	$ 38.35	$ 31.94
President and chief operating officer
Stock options awarded
Nonqualified stock options granted (in shares)					125,000
Number of Stock Options
Add: Options granted (in shares)					125,000
Stock Options
Stock Compensation Plans
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period						10 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period						3 years
Stock-based compensation expense and related income tax benefits
Stock-based compensation expense	$ 1.7
Compensation costs related to equity awards and amounts recognized
Unrecognized compensation cost at the beginning of the period	0.8
Grant date fair value current year grants	1.5
Compensation expense recognized	(1.7)
Unrecognized compensation cost at the end of the period	$ 0.6	$ 0.8
Expected amortization period	1 year 8 months 6 days
Stock options awarded
Number of stock options to be converted(in shares)							545,000
Performance Shares and RSUs
Stock-based compensation expense and related income tax benefits
Stock-based compensation expense	$ 4.1
Compensation costs related to equity awards and amounts recognized
Unrecognized compensation cost at the beginning of the period	1.6
Grant date fair value of current year grants	4.2
Compensation expense recognized	(4.1)
Unrecognized compensation cost at the end of the period	$ 1.7	$ 1.6
Expected amortization period	1 year 6 months 6 days
Options
Fair value assumptions
Expected term in years	5 years 9 months 6 days	5 years 9 months 18 days	5 years 10 months 24 days
Risk free interest rate (as a percent)	1.80%	1.40%	1.90%
Volatility (as a percent)	32.10%	34.40%	36.50%
Dividend yield (as a percent)	3.00%	2.00%	2.20%
Nonqualified stock options
Stock options awarded
Nonqualified stock options granted (in shares)	113,935	87,930	95,670
Per share weighted-average exercise price (in dollars per share)	$ 58.03	$ 59.72	$ 43.17
Per share weighted-average grant date fair value (in dollars per share)	$ 13.51	$ 16.47	$ 12.72
Number of Stock Options
Add: Options granted (in shares)	113,935	87,930	95,670
Weighted-Average Exercise Price
Add: Options granted (in dollars per share)	$ 58.03	$ 59.72	$ 43.17
Nonqualified stock options \| President and chief operating officer
Stock Compensation Plans
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period					10 years
Stock options awarded
Per share weighted-average exercise price (in dollars per share)					$ 24.09
Per share weighted-average grant date fair value (in dollars per share)					9.55
Fair value assumptions
Percentage of awards earned	100.00%
Weighted-Average Exercise Price
Add: Options granted (in dollars per share)					$ 24.09
RSUs \| Non-employee members of the board of directors
Stock Compensation Plans
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	1 year
Omnibus Plan
Stock Compensation Plans
Shares of common stock reserved for future issuance						3,500,000
Par value of shares of common stock (in dollars per share)						$ 0.01
2013 Omnibus Plan
Stock Compensation Plans
Shares of common stock reserved for future issuance	950,000
Additional common stock reserved for issuance subject to shareholders approval (in shares)				1,577,000
Reduction in number of shares available for future issuance (shares)	17,000