Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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.

+ References

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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

+ References

No definition available.

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Unrecognized cost of unvested options awarded to employees as compensation.

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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.

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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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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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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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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.

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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.

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Stockholders' Equity - Additional Information (Detail) - USD ($) shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Apr. 30, 2007
Limited Partners' Capital Account [Line Items]
Total fair value of other stock awards vested	$ 1,647,000		$ 2,654,000
Restricted Stock Awards [Member]
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	729,000	$ 594,000	1,278,000	$ 1,080,000
Stock Options [Member]
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	146,000	160,000	292,000	317,000
Unrecognized stock-based compensation expense	929,000		$ 929,000
Unrecognized stock-based compensation expense, weighted average period			1 year 9 months 18 days
Restricted Stock and Restricted Stock Unit [Member]
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense, weighted average period			1 year 10 months 24 days
Unrecognized stock-based compensation expense	3,316,000		$ 3,316,000
Performance-Based Stock Units [Member]
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense, weighted average period			2 years 6 months
Amended and Restated 1997 Employee Stock Purchase Plan [Member]
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	26,000	$ 21,000	$ 52,000	$ 38,000
Non-Employee Director [Member] \| Restricted Stock Awards [Member]
Limited Partners' Capital Account [Line Items]
Options vesting period			3 years
Minimum [Member] \| 2006 Stock Incentive Plan [Member]
Limited Partners' Capital Account [Line Items]
Options vesting period			1 year
Maximum [Member] \| Performance-Based Stock Units [Member]
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense	$ 442,000		$ 442,000
Maximum [Member] \| 2006 Stock Incentive Plan [Member]
Limited Partners' Capital Account [Line Items]
Options vesting period			4 years
Options granted period			10 years
Class A Common Stock [Member] \| 2006 Stock Incentive Plan [Member]
Limited Partners' Capital Account [Line Items]
Common stock, authorized shares					2,475
Number of shares available for future grant	562		562