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Stock Compensation - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified |
12 Months Ended | 12 Months Ended | ||||||||||
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Apr. 16, 2007
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Jul. 01, 1998
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Apr. 16, 2007
Employee Stock Purchase Plan 1998 [Member]
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Jul. 01, 1998
Employee Stock Purchase Plan 1998 [Member]
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Dec. 31, 2012
CLASS A COMMON STOCK [Member]
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Dec. 31, 2011
CLASS A COMMON STOCK [Member]
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Dec. 31, 2010
CLASS A COMMON STOCK [Member]
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May 31, 2003
CLASS A COMMON STOCK [Member]
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Jun. 30, 2001
CLASS A COMMON STOCK [Member]
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||||||||||
| Number of shares authorized for issuance | 11,215,154 | 8,215,154 | ||||||||||
| Vesting period stock option awards | 3 years | |||||||||||
| Expiration period of stock option awards | 10 years | |||||||||||
| Number of shares reserved for issuance | 7,500,000 | 3,000,000 | 2,781,415 | |||||||||
| Intrinsic value of options exercised | $ 1.9 | $ 1.2 | $ 20.9 | |||||||||
| Stock options granted | 0 | 0 | 0 | |||||||||
| Number of shares remain available for grant | 4,868,881 | |||||||||||
| Unrecognized compensation cost related to unvested stock | 4.7 | 11.3 | ||||||||||
| Weighted average period for recognition of cost | 3 years 8 months 12 days | 10 months 24 days | ||||||||||
| Total fair value of shares vested | 13.1 | 13.9 | ||||||||||
| Period utilized to implement employee stock purchase plan | 6 months | |||||||||||
| Interval for purchases occurring | 6 months | |||||||||||
| Eligibility to Participate Stock Purchase Plan | At least 20 hours per week and more than five months in any calendar year | |||||||||||
| Maximum percentage of employee's compensation to purchase common stock | 15.00% | 15.00% | ||||||||||
| Percentage of price of common stock purchased | 85.00% | 85.00% | ||||||||||
| Proceeds from issuance of common stock under the employee stock purchase plan, Shares | 186,199 | 178,189 | 103,430 | 186,000 | 178,000 | 103,000 | ||||||
| Proceeds from issuance of common stock under the employee stock purchase plan | $ 2.4 | $ 2.0 | $ 2.1 | |||||||||
| X | ||||||||||
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- Definition
Eligibility to participate stock purchase plan. No definition available.
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- Definition
Interval for Purchases occurring. No definition available.
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| X | ||||||||||
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- Definition
Maximum percentage of employee's compensation to purchase common stock. No definition available.
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| X | ||||||||||
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- Definition
Percentage of price of common stock purchased. No definition available.
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| X | ||||||||||
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- Definition
Period utilized to implement employee stock purchase plan. No definition available.
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| X | ||||||||||
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- Definition
Aggregate number of common shares reserved for future issuance. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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| X | ||||||||||
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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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Net number of share options (or share units) granted during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Number of shares issued during the period as a result of an employee stock purchase plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Aggregate change in value for stock issued during the period as a result of employee stock purchase plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan. No definition available.
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