Stock-Based Compensation (Details Textual) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011
Stock-Based Compensation (Textual) [Abstract]
Award vesting terms	vesting terms ranging from three to five years and include 1) options that vest in one-fifth increments beginning on the grant date and continuing on each of the first four anniversaries of the grant date and 2) options that cliff-vest on the fifth anniversary of the grant date
Non cash compensation expense	$ 7,033	$ 4,678
Maximum [Member]
Stock-Based Compensation (Textual) [Abstract]
Award vesting period	5 years
Range of awards of target number of share	100.00%
Minimum [Member]
Stock-Based Compensation (Textual) [Abstract]
Award vesting period	3 years
Range of awards of target number of share	0.00%
Common Class A [Member]
Stock-Based Compensation (Textual) [Abstract]
The Company granted options for an aggregate shares of its Class A common stock	36,500
Performance Based Compensation [Member]
Stock-Based Compensation (Textual) [Abstract]
Non cash compensation expense	3,226
1996 Equity Incentive Plan [Member] \| Common Class A [Member]
Stock-Based Compensation (Textual) [Abstract]
Equity Incentive Plan has reserved shares of Class A common stock	13,000,000
Restricted Stock Award [Member]
Stock-Based Compensation (Textual) [Abstract]
Expiration date of options granted under equity incentive plan	10 years
Percentage of awards vesting on grant date	50.00%
Percentage of awards vesting on the last day of directors term	50.00%
Term of director	1 year
Restricted Stock Award [Member] \| Common Class A [Member]
Stock-Based Compensation (Textual) [Abstract]
Non cash compensation expense	$ 184
2009 Employee Stock Purchase Plan [Member]
Stock-Based Compensation (Textual) [Abstract]
New employee stock purchase plan, which reserved additional shares of common stock	588,154
2009 Employee Stock Purchase Plan [Member] \| Common Class A [Member]
Stock-Based Compensation (Textual) [Abstract]
New employee stock purchase plan, which available for issuance of common stock	88,154
Increase in the additional shares of Class A common stock	77,928
Addition to the increased number of shares of Class A common stock	250,000

Total shares reserved by the new employee stock purchase plan.

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- Definition

Percentage of awards vesting on grant date.

+ References

No definition available.

+ Details

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- Definition

Percentage of awards vesting on last day of directors term.

+ References

No definition available.

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- Definition

Range of awards of target number of share.

+ References

No definition available.

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- Definition

Share-based compensation arrangement by share-based payment award expiration period.

+ References

No definition available.

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- Definition

Additional shares reserved by amendment to the employee stock purchase plan.

+ References

No definition available.

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- Definition

Shares reserved under the automatic increase provisions of the employee stock purchase plan.

+ References

No definition available.

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- Definition

Shares remaining outstanding for issuance when additional shares were reserved for issuance.

+ References

No definition available.

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- Definition

Term of director.

+ References

No definition available.

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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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

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- Definition

Description of the period of time over 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, which may be expressed in a variety of ways (for example, in years, month and year).

+ 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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

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

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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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(3)

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

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- Definition

Net number of share options (or share units) granted during the period.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(d)

-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 (c)(1)(iv)(1)

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

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- Definition

Description of pertinent provisions of equity-based compensation awards that have actual or potential impact upon the company's financial statements.

+ 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

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

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