STOCK INCENTIVE PLANS (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
STOCK INCENTIVE PLANS
Aggregate shares of common stock authorized for issuance to certain employees under the 2007 (adopted in 2006) stock incentive plans	6,000,000
Plan expiration period from the date of inception (in years)	10
Shares available for future grants under 2007 (adopted in 2006) stock incentive plans	4,378,338	4,541,522	5,674,004
Stock options
Share-based Compensation Arrangement by Share-based Payment Award
Stock options exercisable period from date of grant, maximum (in years)	10
Stock options maximum vesting period for Company employees other than directors (in years)	three years
Portion of stock options vested per year for Company employees other than directors	one-third per year
Aggregate Intrinsic Value
Options exercisable at the beginning of the period (in dollars)	$ 1,991	$ 6,860	$ 5,467
Options exercised, aggregate intrinsic value (in dollars)	1,389	5,988	4,906
Options exercisable at the end of the period (in dollars)	$ 402	$ 1,991	$ 6,860	$ 5,467
Number of Options
Options exercisable at the beginning of the period (in shares)	250,946	826,182	1,389,338
Options exercised (in shares)	(173,506)	(575,236)	(563,156)
Options exercisable at the end of the period (in shares)	77,440	250,946	826,182	1,389,338
Per Share Option Price Range
Stock options outstanding and exercisable, range of exercise prices, low end of range (in dollars per share)	$ 24.82	$ 22.04	$ 16.78	$ 15.86
Stock options outstanding and exercisable, range of exercise prices, high end of range (in dollars per share)	$ 26.95	$ 26.95	$ 26.95	$ 26.95
Stock options, exercised price, low end of range (in dollars per share)	$ 22.04	$ 16.78	$ 15.86
Stock options, exercised price, high end of range (in dollars per share)	$ 25.22	$ 24.82	$ 17.44
Weighted-Average Exercise Price Per Option
Options exercisable, weighted-average exercise price (in dollars per share)	$ 24.88	$ 24.72	$ 21.35	$ 19.75
Options exercised, weighted-average exercise price (in dollars per share)	$ 24.65	$ 19.87	$ 17.40
Weighted-average remaining contractual life of stock options outstanding and exercisable (in years)	1.0