Summary of MSU Performance (Details) (Market Performance Based Restricted Stock Units, USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Dec. 31, 2011
Market Performance Based Restricted Stock Units
Number of Shares Underlying MSUs
Nonvested as of December 31, 2012		266
Granted	220
Vested and released	(79)
Forfeited	(32)
Nonvested as of March 31, 2013	375	266
Weighted Average Remaining Vesting Period
Nonvested as of March 31, 2013	2 years 3 months 18 days
Aggregate Intrinsic Value
Nonvested as of March 31, 2013	$ 12,553

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Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other Than Options, Outstanding, Intrinsic Value

+ References

No definition available.

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- Definition

Share based Compensation Arrangement by Share based Payment Award, Equity Instruments Other than Options, Outstanding, Weighted Average Remaining Contractual Term 1

+ References

No definition available.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

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- Definition

The number of grants made 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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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(b)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(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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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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