Stock-Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
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	$ 11,387	$ 10,513
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration date of options granted under equity incentive plan	10 years
Term of director	1 year
Restricted Stock [Member] \| Percentage of awards vesting on grant date [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of awards vesting on grant date	50.00%
Restricted Stock [Member] \| Percentage of Awards Vesting On Last Day of Directors Term [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of awards vesting on grant date	50.00%
Common Class A [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
The Company granted options for an aggregate shares of its Class A common stock	23,000
Common Class A [Member] \| 1996 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
New employee stock purchase plan, which reserved additional shares of common stock	15,500,000
Common Class A [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non cash compensation expense	$ 229
Common Class A [Member] \| 2009 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
New employee stock purchase plan, which reserved additional shares of common stock	588,154
Employee stock purchase plan, which available for issuance of common stock	88,154
Additional shares reserved under 2009 ESPP	80,932
Performance Based Compensation [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non cash compensation expense	$ 6,355
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Range of awards of target number of share	0.00%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	5 years
Range of awards of target number of share	100.00%

Range of awards of target number of share.

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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.

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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 Accounting Standards Codification

-Topic 230

-SubTopic 10

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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.

+ References

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

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Number of additional shares authorized for issuance under an established share-based compensation plan.

+ References

No definition available.

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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

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- Definition

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

+ References

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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

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- Definition

Percentage of vesting of share-based compensation awards.

+ References

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- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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