Stock-Based Compensation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012
Stock-Based Compensation Arrangement Rollforward
Restricted stock used for tax withholding	769
Common Class A
Stock-Based Compensation Arrangement Rollforward
Restricted stock used for tax withholding	769
Phantom Shares \| Phantom Stock Plan
Stock-Based Compensation [Line Items]
Maximum percentage of fair market value of the Company available for share-based awards	2.00%
Maximum individual award as a percentage of shares available for award	5.00%
Days from vesting date to cash settlement	120 days
Stock-Based Compensation Arrangement Rollforward
Unvested and outstanding at beginning of period	$ 16.87
Unvested and outstanding at beginning of period (in shares)	84,764
Granted	$ 0.00
Granted (in shares)	0
Vested	$ 16.20
Vested (in shares)	(21,260)
Vest Date Fair Value	$ 273
Forfeited	$ 17.83
Forfeited (in shares)	(4,256)
Unvested and outstanding at end of period	$ 17.05
Unvested and outstanding at end of period (in shares)	59,248
Phantom Shares \| Time Vested \| Phantom Stock Plan
Stock-Based Compensation [Line Items]
Award vesting period	5 years
Restricted Stock Units (RSU) \| Non-Officer Restricted Stock Unit Plan
Stock-Based Compensation [Line Items]
Maximum percentage of fair market value of the Company available for share-based awards	2.00%
Days from vesting date to cash settlement	120 days
Stock-Based Compensation Arrangement Rollforward
Unvested and outstanding at beginning of period	$ 17.12
Unvested and outstanding at beginning of period (in shares)	151,909
Granted	$ 12.83
Granted (in shares)	248,361
Vested	$ 17.84
Vested (in shares)	(43,354)
Vest Date Fair Value	556
Forfeited	$ 14.44
Forfeited (in shares)	(24,798)
Unvested and outstanding at end of period	$ 14.02
Unvested and outstanding at end of period (in shares)	332,118
Phantom Stock and RSU \| Phantom Stock Plan And Restricted Stock Unit Plan
Stock-Based Compensation Arrangement Rollforward
Estimated fair value per share at end of period	$ 10.19
Aggregate intrinisc value of unvested Time Vested restricted shares	3,988
Restricted Stock \| 2010 Equity Incentive Plan \| Common Class A
Stock-Based Compensation Arrangement Rollforward
Shares reserved for issuance under the 2010 Plan	86,301
Restricted stock used for tax withholding	769	643
Shares expected to be repurchased during the next twelve months	2,000
Restricted Stock \| Time Vested \| 2010 Equity Incentive Plan \| Common Class A
Stock-Based Compensation Arrangement Rollforward
Unvested and outstanding at beginning of period	$ 651.97
Unvested and outstanding at beginning of period (in shares)	9,481
Granted	$ 626.02
Granted (in shares)	2,518
Vested	$ 681.36
Vested (in shares)	(1,950)
Vest Date Fair Value	1,206
Forfeited	$ 622.32
Forfeited (in shares)	(1,257)
Modified	$ 626.00
Modified (in shares)	11,166
Unvested and outstanding at end of period	$ 633.16
Unvested and outstanding at end of period (in shares)	19,958
Estimated fair value per share at end of period	$ 626.00
Aggregate intrinisc value of unvested Time Vested restricted shares	$ 12,494
Restricted Stock \| Market and Performance Vesting Conditions \| 2010 Equity Incentive Plan \| Common Class A
Stock-Based Compensation Arrangement Rollforward
Unvested and outstanding at beginning of period	$ 324.48
Unvested and outstanding at beginning of period (in shares)	55,824
Granted	$ 181.59
Granted (in shares)	4,733
Vested	$ 0.00
Vested (in shares)	0
Forfeited	$ 335.72
Forfeited (in shares)	(2,203)
Modified	$ 324.47
Modified (in shares)	(11,166)
Unvested and outstanding at end of period	$ 309.62
Unvested and outstanding at end of period (in shares)	47,188
Maximum \| Restricted Stock Units (RSU)
Stock-Based Compensation [Line Items]
Award vesting period	3 years
Maximum \| Restricted Stock \| Time Vested \| 2010 Equity Incentive Plan
Stock-Based Compensation [Line Items]
Award vesting period	5 years
Maximum \| Restricted Stock \| Performance Vested \| 2010 Equity Incentive Plan
Stock-Based Compensation [Line Items]
Award vesting period	5 years

Maximum Individual Award, Percentage Of The Total Shares Available For Award Under Plan

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Modifications, Weighted Average Grant Date Fair Value

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Modified in Period

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Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Aggregate Intrinsic Value

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Share-Based Compensation Arrangement By Share-Based Payment Award, Period From Vesting Date Before Award Is Cash Settled

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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.

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

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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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).

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The weighted average fair value at grant date for nonvested equity-based awards issued 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).

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The intrinsic value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units, as calculated by applying the disclosed pricing methodology.

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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.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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

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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.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan 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.

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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).

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Maximum number of shares that may be issued in accordance with the plan as a proportion of outstanding capital stock.

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No definition available.

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- Definition

An entity expecting to repurchase shares in the following period, generally discloses an estimate of the amount or range of shares to be repurchased.

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- Definition

For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

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