Stock Options - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of unissued common shares available for grant under the plans	3.2
Share-based compensation expense recognized	$ 10.8	$ 11.8
Cash received from stock options exercised	4.5	0.4
Performance Based Unit \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares which will vest after achievement of goals	0
Performance Based Unit \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares which will vest after achievement of goals	1.5
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense recognized	2.7	4.7
Total unrecognized compensation cost	1.8
Recognition period for remaining unrecognized compensation expense, weighted-average period	2 years 1 month 6 days
Aggregate weighted-average grant-date fair value of units granted	5.0	3.2
Aggregate weighted-average grant-date fair value of units vested	4.3	4.1
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense recognized	8.1	7.1
Total intrinsic value of options exercised	5.7	0.8
Total unrecognized compensation cost	$ 4.2
Recognition period for remaining unrecognized compensation expense, weighted-average period	1 year 6 months

Share Based Compensation Arrangement By Share Based Payment Award Number of Shares Vesting After Achievement of Goals

No definition available.

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- Definition

Share-based compensation arrangement by share-based payment award, other than options, grants in period, weighted average grant date fair value.

+ References

No definition available.

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- Definition

Share-based compensation arrangement by share-based payment award, other than options, vested in period, weighted average grant date fair value.

+ References

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 50

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-Section S99

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

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- Definition

Aggregate proceeds received by the entity during the annual period from exercises of stock or unit options and conversion of similar instruments granted under equity-based payment arrangements.

+ References

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-Publisher FASB

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

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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 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.

+ References

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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.

+ References

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-Publisher FASB

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