SECURITIES REPURCHASE PROGRAM (Details) (USD $)	3 Months Ended			3 Months Ended		1 Months Ended				3 Months Ended		1 Months Ended	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012 ValueAct Capital Master Fund, L.P. ( ValueAct )	Mar. 31, 2012 5.375% Convertible Notes due in August, 2014	Mar. 31, 2011 5.375% Convertible Notes due in August, 2014	Aug. 31, 2011 Securities Repurchase Program	Mar. 31, 2011 Securities Repurchase Program	Nov. 30, 2010 Securities Repurchase Program	Mar. 31, 2011 Securities Repurchase Program ValueAct Capital Master Fund, L.P. ( ValueAct )	Mar. 31, 2011 Securities Repurchase Program ValueAct Capital Master Fund, L.P. ( ValueAct )	Mar. 31, 2011 Securities Repurchase Program 5.375% Convertible Notes due in August, 2014	Nov. 30, 2011 New Securities Repurchase Program	Mar. 31, 2012 New Securities Repurchase Program	Mar. 31, 2012 New Securities Repurchase Program 5.375% Convertible Notes due in August, 2014	Mar. 31, 2012 New Securities Repurchase Program 5.375% Convertible Notes due in August, 2014 Stock Repurchased Subsequent to Period End
Securities Repurchase Program
Aggregate maximum amount authorized under the Securities Repurchase Program						$ 1,800,000,000		$ 1,500,000,000				$ 1,500,000,000
Increased authorized amount under the Securities Repurchase Program						300,000,000
Aggregate principal amount of notes repurchased											52,300,000			1,100,000
Stated interest rate (as a percent)					5.375%
Aggregate purchase price of convertible notes	3,975,000	139,225,000		3,900,000	139,200,000						141,500,000			4,000,000
Carrying amount of convertible notes				1,000,000	44,700,000
Unamortized deferred financing costs					1,500,000
Estimated fair value of convertible notes				1,100,000	53,000,000
Loss on extinguishment of debt	133,000	8,262,000		100,000	8,300,000
Difference between the estimated fair value and the repurchase price of securities				2,900,000	88,500,000
Difference between the estimated fair value and the purchase price of securities charged to additional paid-in capital				200,000	8,500,000
Difference between the estimated fair value and the purchase price of securities charged to accumulated deficit				2,700,000	80,000,000
Accreted interest on repurchase of convertible debt	56,000	2,289,000		100,000	2,300,000
Premium above the carrying value on repurchase of convertible debt				1,900,000
Common shares repurchased									7,366,419
Aggregate repurchase price of the entity's common shares repurchased	108,724,000	274,750,000							274,800,000				108,700,000		51,800,000
Discount rate applied for repurchases of shares (as a percent)									5.77%
Number of trading days used in calculation of discount rate to be applied for repurchases of shares									20 days	20 days
Excess of repurchase price over carrying value of securities repurchased, charged to accumulated deficit							146,800,000						69,700,000
Estimated amount receivable in relation to withholding taxes on repurchase			24,200,000
Convertible notes, senior notes and shares repurchased													$ 270,500,000
Shares repurchased													2,004,952		949,466