Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	2.5
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 10.54
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number	0.9
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost	$ 4.8	$ 6.7	$ 6.1
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ 2.2	$ 2.2	$ 1.6
Exercisable at end of year (shares)	1.6	1.4	1.2
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value	$ 12.9
Shares authorized under stock compensation plans	7.8
Shares authorized under stock compensation plans	Apr. 30, 2025
Stock options vesting period	3 years
Weighted average fair value of options granted (usd per share)	$ 4.25	$ 6.12	$ 7.16
Aggregate intrinsic value of stock options outstanding	$ 10.8
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	0.4	$ 0.8	$ 2.0
Proceeds from stock compensation activity	0.5	1.0	$ 2.6
Percentage of target shares earned			200.00%
Excess tax benefit from stock-based compensation	0.0	1.6	$ 2.2
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options	0.1	0.2	0.8
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	1.3	1.3	0.6
Compensation expense related to share-based compensation plans	1.2	1.2	1.0
Unrecognized compensation cost related to stock options	$ 0.8
Weighted-average recognition period for unrecognized compensation cost	1 year 10 months 28 days
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense related to share-based compensation plans	$ 2.1	2.0	1.7
Unrecognized compensation cost related to stock options	$ 2.8
Weighted-average recognition period for unrecognized compensation cost	1 year 10 months 28 days
PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	$ 3.7	3.7	2.5
Compensation expense related to share-based compensation plans	1.5	$ 3.5	$ 3.4
Unrecognized compensation cost	$ 1.1
Weighted-average recognition period for unrecognized compensation cost	2 years
Minimum \| PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock, percent	0.00%
Maximum \| PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock, percent	200.00%
2013 Grants \| PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options vesting period	3 years
2014 Grants \| PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options vesting period	3 years
Performance share units performance period	2 years
Service requirement	1 year
Percentage of target shares earned	200.00%
2015 Grants \| PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options vesting period	3 years
Performance-based Restricted Stock Units, 2016 Grants [Member] \| PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance share units performance period	3 years

Percentage Of Target Shares

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Share Based Compensation Arrangement By Share Based Payment Award, Grant Date Expiration, Month and Year

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Share Based Compensation Arrangement by Share Based Payment Award, Performance Period

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Share-based Compensation Arrangement by Share-based Payment Award, Options, Expected to Vest, Outstanding, Number

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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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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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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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Unrecognized cost of unvested options awarded to employees as compensation.

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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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Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period.

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Amount of cash outflow for realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes.

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The total cash inflow associated with the amount received from holders to acquire the entity's shares under incentive and share awards, including stock option exercises. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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Amount of capitalized and expensed compensation cost from equity-based compensation arrangements.

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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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Purchase price of common stock expressed as a percentage of its fair value.

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