STOCK-BASED COMPENSATION (Details 4) (USD $)	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2009
Restricted and deferred stock units
Shares
Outstanding at the beginning of the period (in shares)	909,358
Granted (in shares)	290,003	154,048	2,274,745
Vested and released (in shares)	(399,212)
Forfeited (in shares)	(7,334)
Outstanding at the end of the period (in shares)	792,815	909,358
Vested or expected to vest at the end of the period (in shares)	700,019
Weighted Average Remaining Contractual Terms
Outstanding at the end of the period (in years)	2.3
Vested or expected to vest at the end of the period (in years)	2.3
Weighted Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 10.75
Granted (in dollars per share)	$ 27.55	$ 16.37	$ 8.75
Vested and released (in dollars per share)	$ 10.57
Forfeited (in dollars per share)	$ 8.75
Outstanding at the end of the period (in dollars per share)	$ 17.00	$ 10.75
Vested or expected to vest at the end of the period (in dollars per share)	$ 15.64
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	$ 15,452,000
Vested or expected to vest at the end of the period (in dollars)	$ 13,643,000
Minimum vesting period (in years)	P1Y
Maximum vesting period (in years)	P3Y
Total intrinsic value of share awards vested (in dollars)	$ 8,100,000	$ 5,600,000	$ 20,100,000
Restricted stock surrendered in satisfaction of required minimum tax withholding obligations (in shares)	126,934	128,654	396,906
PRSUs
The weighted average assumptions used in the Monte Carlo simulation model
Risk-free interest rate (as a percent)	0.95%
Expected life (in years)	3
Expected volatility (as a percent)	45.00%
Expected dividend yield (as a percent)	0.00%
PRSUs | Minimum
Aggregate Intrinsic Value
Percentage multiplied to target award for determining the number of shares subject to award	0.00%
PRSUs | Maximum
Aggregate Intrinsic Value
Percentage multiplied to target award for determining the number of shares subject to award	150.00%