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

Unrecognized cost of unvested share-based compensation awards.

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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.

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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

Net number of non-option equity instruments granted to participants.

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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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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

Expected term of share-based compensation awards, 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 of outstanding stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

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Payment Of Withholding Taxes Related To Restricted Stock

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Stock-based Compensation - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance (in shares)	306,275		306,275
Shares of common stock reserved for issuance (in shares)	1,800,000		1,800,000
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share settlement under RSUs (in shares)			37,488	50,952
Cash used for employee withholding tax payments			$ 5.1	$ 9.5
Unamortized stock-based compensation expense	$ 19.3		$ 19.3
Weighted-average remaining amortization period			1 year 10 months 24 days
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual life			10 years
Vesting period			3 years
Stock-based compensation expense	$ 2.7	$ 2.5	$ 9.2	$ 7.0
RSU and Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company granted performance contingent RSU (in shares)			33,632	30,101
Stock-based compensation expense			$ 1.8	$ 0.9
Minimum [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual life			1 year
Maximum [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual life			3 years