STOCK BASED COMPENSATION - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2005	May 31, 2001	Dec. 31, 2000	Dec. 31, 1997	Dec. 31, 1996
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based payment award, number of shares authorized	3,000,000			3,500,000	4,800,000	600,000	7,000,000	6,000,000	2,340,000
Employee stock purchase plan, description	The ESPP authorizes 600,000 shares of our common stock to be purchased by employees at a 15% discount from the market price of the stock through payroll deductions during two six-month offerings each year. An employee who elects to participate in an offering is granted an option on the first day of the offering for a number of shares equal to the employee's payroll deductions under the ESPP during the offering period (which may not exceed $5,000) divided by the option price per share. The option price per share is the lower of 85% of the closing price of a share of our common stock on the first trading day of the offering period or 85% of the closing price on the last trading day of the offering period. We recognize compensation expense for the ESPP, which is reflected in the statement of income. Every U.S. employee who has completed six months employment as of the first day of an offering and who is a full-time employee, or a part-time employee who customarily works at least 20 hours per week, is eligible to participate in the offering.
Employee stock purchase plan, percentage of discount to market price	15.00%
Employee stock purchase plan, maximum payroll deductions						$ 5,000
Employee stock purchase plan, option price as a percentage of closing stock price	85.00%
Stock issued under employee stock purchase plan	53,213	61,573	56,145
Stock-based compensation expense	15,367,000	15,298,000	14,638,000
Expected dividend yield	0.00%	0.00%	0.00%
Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock purchase plan, service period to be eligible	Six months
Part Time Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock purchase plan, service period to be eligible	20 hours per week
Stock option plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	14,400,000	14,400,000	14,000,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,000,000	900,000	700,000
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Per share fair value of RSUs	$ 85.00	$ 51.65
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expenses	$ 24,500,000
Weighted average period for recognition of compensation expense	1.49
Stock option, maximum term	10 years
Stock Options | Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period	1 year
Stock Options | Officers and employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period	5 years