Stock-Based Compensation (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2012 Y	Mar. 31, 2011
2008 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for issuance	19,300,000
Number of shares available for grant	4,800,000
Restricted Stock Unit Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total fair value of RSU awards vested	$ 1.3	$ 2.7
Minimum vesting period of outstanding RSU awards (years)	3
Unrecognized stock-based compensation cost	2.0
Weighted-average recognized period (years)	0.8
Stock Option Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%
Employee Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value of options granted	$ 6.75	$ 9.22
Total intrinsic value of options exercised	5.1	6.6
Total fair value of options vested	12.6	11.3
Unrecognized stock-based compensation cost	$ 46.9
Weighted-average recognized period (years)	4.1
Expected dividend yield
Employee Stock Options [Member] \| 2008 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock issued	1
Restricted Stock Award [Member] \| 2008 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock issued	1.94

For each of common stock share, reduction of the reserved shares for issuance.

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested

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- Definition

Share-based compensation arrangement by share-based payment award, options, vested in period, fair value

+ References

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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.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph h

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (i)

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- Definition

The weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, using a decimal to express in number of years.

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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.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph e(2)(c)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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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).

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

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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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-Topic 718

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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.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph c(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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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.

+ References

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-Publisher FASB

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