Performance Metric, Potential Range

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- Definition

Share-based compensation arrangement by share-based payment award, increase as grant in period, percentage

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No definition available.

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- Definition

Share-based Compensation Arrangement by Share-Based Payment Award, Options, Tax Expense Realized from Options Exercised

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No definition available.

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- Definition

Share-based compensation arrangement by share-based payment award, reduction in shares available for grant per share issued.

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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.

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- Definition

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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No definition available.

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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.

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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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- Definition

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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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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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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- Definition

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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- Definition

Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

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.

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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.

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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

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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- Definition

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

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No definition available.

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- Definition

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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- Definition

Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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- Definition

Percentage of vesting of share-based compensation awards.

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- Definition

Intrinsic value of equity-based compensation awards outstanding. Excludes stock and unit options.

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No definition available.

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- Definition

Intrinsic value of equity-based compensation awards vested. Excludes stock and unit options.

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No definition available.

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- Definition

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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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Stock-based Compensation Plans (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended			55 Months Ended
	May 20, 2014	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 28, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Arrangement by Share Based Payment Award, Reduction in Shares Available for Grant Per Share Issued	3.8
Shares awarded		301,152	460,610	587,340
Stock-based compensation expense		$ 14.9	$ 10.5	$ 10.5
Tax benefit from compensation expense		$ 3.1	3.7	3.7
Vesting period		3 years
Award expiration Period		10 years
Cash received for options exercised		$ 14.8	23.1	16.2
Intrinsic value of options exercised		9.6	15.6	21.1
Share-based Compensation Arrangement by Share-Based Payment Award, Options, Tax Expense Realized from Options Exercised		1.6	$ 4.0	$ 5.6
Aggregate intrinsic value, outstanding		34.1
Aggregate intrinsic value, exercisable		$ 24.2
Weighted average remaining contractual life, outstanding (in years)		7 years 6 months
Weighted average remaining contractual life, exercisable (in years)		6 years 2 months 12 days
Weighted average grant date fair value of options granted		$ 16.30	$ 13.05	$ 10.83
Fair value of vested shares		$ 9.3	$ 8.3
Vesting Each Year [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting rate		33.33%	33.33%	33.33%
Chaucer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense			$ 1.2	$ 1.0
Option or SAR
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Arrangement by Share Based Payment Award, Reduction in Shares Available for Grant Per Share Issued	1
Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense		$ 3.7
Unrecognized compensation expense, weighted average period of recognition		1 year 6 months
Market-Based Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		3 years	3 years	3 years
Forfeited, Shares		10,330	53,840	63,740
Aggregate intrinsic value		$ 8.2
Weighted average remaining contractual life		1 year 4 months 24 days
Market-Based Restricted Stock Units [Member] \| 2015 Grants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted, Shares		3,115
Increase as grant in period, percentage		100.00%
Granted, Weighted Average Grant Date Fair Value		$ 70.24
Market-Based Restricted Stock Units [Member] \| 2014 Grants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted, Shares			5,881
Granted, Weighted Average Grant Date Fair Value			$ 56.45
Market-Based Restricted Stock Units [Member] \| 2014 and 2013 Grants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase as grant in period, percentage			100.00%
Time-based Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		3 years	3 years	3 years
Market-based awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		3 years
Granted, Shares		31,688	56,571	87,213
Performance And Market-Based Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense		$ 19.7
Unrecognized compensation expense, weighted average period of recognition		1 year 9 months 18 days
Intrinsic value of awards vested		$ 0.6	$ 0.6	$ 5.8
Performance And Market-Based Restricted Stock Units \| 2014 Grants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted, Shares				2,268
Granted, Weighted Average Grant Date Fair Value				$ 57.00
Performance And Market-Based Restricted Stock Units \| 2013 Grants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted, Shares				30,134
Granted, Weighted Average Grant Date Fair Value				$ 41.77
Performance And Market-Based Restricted Stock Units \| Minimum [Member] \| Senior management
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Performance metric, potential range		0.00%
Performance And Market-Based Restricted Stock Units \| Maximum [Member] \| Senior management
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Performance metric, potential range		150.00%
Restricted Stock and Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value of awards vested		$ 2.9	$ 2.3	$ 5.4
Aggregate intrinsic value		$ 39.1
Weighted average remaining contractual life		1 year 3 months 18 days
Performance-based restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Forfeited, Shares		43,449	1,090
2014 Stock Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized under plan	6,100,000
Number of shares available for grant		4,343,301
ESPP Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized under plan	2,500,000
Number of shares available for grant		2,371,060
SIP Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized under plan	750,000
Shares awarded					74,189
Two Thousand Fourteen Stock Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Cash received for options exercised		$ 14.3	$ 20.5	$ 15.8