Stock-Based Compensation -Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reduction in number of shares available for grant, for every one restricted share or restricted stock unit awarded	2
Shares available to be awarded under the plan	2,441,640
Aggregate intrinsic value of options exercised	$ 1.4	$ 6.5	$ 7.0
Options exercised	36,533
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum aggregate number of shares of common stock that may be issued in connection with stock options, stock appreciation rights, restricted stock, restricted stock units and performance award	6,600,000
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value of restricted stock units granted	$ 42.50	$ 36.98	$ 28.62
Fair value of restricted stock units released	5.7	13.7	4.7
Unrecognized compensation expense related to restricted stock units	16.2
Cost expected to be recognized over a period	2 years 6 months
Restricted stock units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum vesting period for restricted stock units outstanding	5 years
Selling, General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 7.2	$ 7.7	$ 5.8

Reduction in Number of Shares Available for Grant, for Every One Restricted Share or Restricted Stock Unit Awarded

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- Definition

As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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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 aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

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-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

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-Paragraph 28

-Subparagraph (a)

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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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- 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).

+ References

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-Publisher FASB

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-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

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-Number 123R

-Paragraph A240

-Subparagraph c(1)

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- Definition

The total fair value of equity-based awards for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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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

The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

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- Definition

Number of share instruments newly issued under a share-based compensation plan.

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-Name Accounting Standards Codification

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-SubTopic 10

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- Definition

Number of share options (or share units) exercised during the current period.

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-Name Accounting Standards Codification

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-SubTopic 10

-Section S99

-Paragraph 1

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-Name Regulation S-X (SX)

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