STOCKHOLDERS' EQUITY (Details 6) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Common Stock Repurchase Program
Authorized amount under stock repurchase program		$ 500,000,000
Shares of common stock repurchased		28,776,000	11,720,000
Average price of shares repurchased (in dollars per share)		$ 10.57	$ 7.59
Reduction in common stock and additional paid-in capital by stock repurchases, excluding commission		304,236,000	89,216,000
Remaining authorized amount available for stock repurchase		106,800,000
Company ESPP
Assumptions used to estimate the fair value of the Company ESPPs shares
Risk-free interest rate (as a percent)		0.12%	0.18%	0.35%
Expected life (in years)		0.50	0.50	0.50
Expected volatility (as a percent)		46.00%	45.00%	73.00%
Weighted-average fair value of the rights to purchase shares (in dollars per share)		$ 2.70	$ 0.89	$ 0.86
Cash proceeds from the issuance of shares		$ 9,400,000	$ 7,400,000	$ 6,500,000
1991 Employee Stock Purchase Plan
Employee Stock Purchase Plan
Purchase price of the entity's common stock expressed as percentage of fair market value		85.00%
Offering period (in months)		P6M
Percentage of employee's eligible compensation as limitation on purchases		10.00%
Shares purchased		800,000	2,000,000	2,100,000
Average purchase price per share (in dollars per share)		$ 4.85	$ 3.65	$ 3.03
Number of shares available under the plan which have expired in the period	1,900,000
2010 Employee Stock Purchase Plan
Employee Stock Purchase Plan
Shares purchased		700,000
Average purchase price per share (in dollars per share)		$ 8.56
Shares authorized for issuance		25,000,000	25,000,000
Number of shares available for issuances		24,300,000