STOCK-BASED COMPENSATION (Details 3) (USD $)	6 Months Ended
	Jun. 30, 2012 Y	Jun. 30, 2011
Restricted and deferred stock units
Shares
Outstanding at the beginning of the period (in shares)	792,815
Granted (in shares)	373,531	289,003
Vested and released (in shares)	54,467
Forfeited (in shares)	4,557
Outstanding at the end of the period (in shares)	1,107,322
Vested or expected to vest at the end of the period (in shares)	1,100,543
Weighted Average Remaining Contractual Terms
Outstanding at the end of the period (in years)	1.1
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
Granted (in dollars per share)	$ 30.44	$ 27.55
Vested and released (in dollars per share)	$ 24.08
Forfeited (in dollars per share)	$ 19.30
Outstanding at the end of the period (in dollars per share)	$ 21.18
Vested or expected to vest at the end of the period (in dollars per share)	$ 21.13
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	$ 28,425,000
Vested or expected to vest at the end of the period (in dollars)	28,251,000
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)	$ 1,700,000	$ 300,000
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%