STOCK PLANS AND SHARE BASED COMPENSATION (Performance-based Awards and Restricted Stock Units) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2011	Mar. 31, 2010	Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Released at End of Performance Year, Maximum Percentage of Targeted Number			200.00%
Performance-based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of performance-based awards shares released as percentage of target number, minimum			0.00%
Number of performance-based awards shares released as percentage of target number, maximum			200.00%
Award requisite service period			12 months
Reduction in number of shares available for issuance under the 2007 Plan per award granted			2
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Outstanding, shares, beginning of period	85,000	119,000	85,000	119,000	0
Outstanding, weighted-average grant date fair value per share, beginning of period	$ 34.97	$ 18.66	$ 34.97	$ 18.66	$ 0.00
Granted, shares			98,000	92,000	119,000
Granted, weighted-average grant date fair value per share			$ 36.57	$ 34.85	$ 18.66
Vested, shares	(85,000)	(119,000)	(85,000)	(121,000)	0
Vested, weighted-average grant date fair value per share			$ 34.97	$ 18.81	$ 0.00
Forfeited or expired, shares			(98,000)	(5,000)	0
Forfeited or expired, weighted-average grant date fair value per share			$ 36.57	$ 33.59	$ 0.00
Outstanding, shares, end of period			0	85,000	119,000
Outstanding, weighted-average grant date fair value per share, end of period			$ 0.00	$ 34.97	$ 18.66
Outstanding, weighted-average remaining contractual term (in years)			0.00
Outstanding, aggregate intrinsic value			$ 0
Outstanding and expected to vest, shares			0
Vested and expected to vest, weighted-average remaining contractual term (in years)			0.00
Vested and expected to vest, aggregate intrinsic value			0
Grant date fair value of awards released			3,000,000	3,000,000
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards vesting period			4 years
Reduction in number of shares available for issuance under the 2007 Plan per award granted			2
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Outstanding, shares, beginning of period	260,000	13,000	260,000	13,000	0
Outstanding, weighted-average grant date fair value per share, beginning of period	$ 36.30	$ 33.17	$ 36.30	$ 33.17	$ 0.00
Granted, shares			296,000	259,000	13,000
Granted, weighted-average grant date fair value per share			$ 36.04	$ 36.44	$ 33.17
Vested, shares			(64,000)	(4,000)	0
Vested, weighted-average grant date fair value per share			$ 36.26	$ 33.94	$ 0.00
Forfeited or expired, shares			(34,000)	(8,000)	0
Forfeited or expired, weighted-average grant date fair value per share			$ 37.13	$ 36.94	$ 0.00
Outstanding, shares, end of period			458,000	260,000	13,000
Outstanding, weighted-average grant date fair value per share, end of period			$ 36.08	$ 36.30	$ 33.17
Outstanding, weighted-average remaining contractual term (in years)			1.60
Outstanding, aggregate intrinsic value			15,175,000
Outstanding and expected to vest, shares			411,000
Vested and expected to vest, weighted-average remaining contractual term (in years)			1.59
Vested and expected to vest, aggregate intrinsic value			13,627,000
Grant date fair value of awards released			$ 2,300,000	$ 200,000