Stock-Based Compensation--Variables and Assumptions Used to Value Restricted Stock Awards (Details) (2010 Equity Incentive Plan [Member], Restricted Stock [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Time Vested [Member] \| Class A Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Discount for lack of control	0.00%	0.00%	23.00%
Discount for lack of marketability	20.00%	17.00%	22.00%
Performance Vested [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate, minimum	0.25%	0.16%	0.25%
Risk free interest rate, maximum	1.48%	2.46%	1.21%
Expected volatility, minimum	52.00%	38.00%	42.00%
Expected volatility, maximum	56.00%	39.00%
Expected volatility			50.00%
Expected life	4 years	5 years	6 years
Expected dividends	0	0	0

Stock-Based Compensation--Variables and Assumptions Used to Value Restricted Stock Awards (Details) (2010 Equity Incentive Plan [Member], Restricted Stock [Member], USD $)
In Thousands, unless otherwise specified

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Time Vested [Member] | Class A Common Stock [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Discount for lack of control

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Performance Vested [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

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Expected volatility, minimum

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Expected volatility, maximum

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Expected volatility

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Expected life

4 years

5 years

6 years

Expected dividends

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- Definition

Percentage above fair value that an investor seeking to acquire control of an entity will pay, used as an input to measure fair value.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bbb)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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Adjustment to the discount rate used to measure fair value for lack of ability to convert business interests into cash quickly.

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- Definition

The estimated amount of dividends to be paid to holders of the underlying shares (expected dividends) over the option's term. Dividends are taken into account because payment of dividends to shareholders reduces the fair value of the underlying shares, and option holders generally do not receive dividends.

+ 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 (f)(2)(iii)

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- Definition

Expected term of share-based compensation awards, 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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 14.D.2)

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-Topic 718

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section D

-Subsection 2

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- Definition

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-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

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-Subparagraph (f)(2)(ii)

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- Definition

The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

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- Definition

The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

No definition available.

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- Definition

The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

No definition available.

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- Definition

The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

No definition available.

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