STOCK-BASED COMPENSATION (Details 3) (USD $)	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Restricted and deferred stock units
Stock-based compensation
Vesting period (in years)	3 years
Shares
Outstanding at the beginning of the period (in shares)	792,815
Vested and released (in shares)	(3,975)
Outstanding at the end of the period (in shares)	788,840
Vested or expected to vest at the end of the period (in shares)	787,168
Weighted Average Remaining Contractual Terms
Outstanding at the end of the period (in years)	1.0
Vested or expected to vest at the end of the period (in years)	1.0
Weighted Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 17.00
Vested and released (in dollars per share)	$ 17.62
Outstanding at the end of the period (in dollars per share)	$ 17.00
Vested or expected to vest at the end of the period (in dollars per share)	$ 16.98
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	$ 27,515,000
Vested or expected to vest at the end of the period (in dollars)	$ 27,456,000
Restricted stock units
Aggregate Intrinsic Value
Minimum vesting period (in years)	P1Y
Maximum vesting period (in years)	P3Y
Total intrinsic value of share awards vested (in dollars)	$ 100,000	$ 200,000
PRSUs \| Maximum
Aggregate Intrinsic Value
Percentage of share awards granted to officers and non-officer employees that vested	150.00%
PRSUs \| Minimum
Aggregate Intrinsic Value
Percentage of share awards granted to officers and non-officer employees that vested	0.00%

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- Definition

As of the balance sheet date, the total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices of fully vested and expected to vest equity-based awards other than stock (or unit) option plans.

+ References

No definition available.

+ Details

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As of the balance sheet date, the number of shares under equity-based payment instruments, excluding stock (or unit) options that are vested or expected to vest.

+ References

No definition available.

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As of the balance sheet date, the weighted-average grant date fair value for outstanding equity-based awards other than stock (or unit) option plans that are fully vested or expected to vest.

+ References

No definition available.

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- Definition

The weighted average period between the balance sheet date and expiration date for fully vested and expected to vest equity-based awards other than stock (or unit) option plans.

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

As of the balance sheet date, the total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices of equity-based awards other than stock (or unit) option plans that vested during the period.

+ References

No definition available.

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- Definition

Description of the period of time over 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, which may be expressed in a variety of ways (for example, in years, month and year).

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The maximum vesting term over 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.

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No definition available.

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The minimum vesting term over 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.

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No definition available.

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- Definition

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.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(a)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(b)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

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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- Definition

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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- Definition

The weighted average period between the balance sheet date and expiration for equity-based awards other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan), which may be expressed in a decimal value for number of years.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Section 50

-Paragraph 2

-Subparagraph (e)(1)

-SubTopic 10

-Topic 718

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

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

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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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