NET INCOME PER SHARE (Details) (USD $)	12 Months Ended										12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Outstanding Stock Awards	Dec. 31, 2011 Outstanding Stock Awards	Dec. 31, 2010 Outstanding Stock Awards	Dec. 31, 2012 Convertible Debt.	Dec. 31, 2011 Convertible Debt.	Dec. 31, 2010 Convertible Debt.	Dec. 31, 2006 Convertible Debt 0.75 Percent Due September 2013 [Member]	Dec. 31, 2006 Convertible Debt Due 2013 [Member]	Dec. 31, 2010 Convertible Debt 0.50 Percent Due September 2011 [Member]	Dec. 31, 2006 Convertible Debt 0.50 Percent Due September 2011 [Member]
Anti-dilutive Securities Excluded From Computation Of Earnings Per Share
Weighted average number of basic common shares outstanding (in shares)	49,840,000	49,654,000	47,955,000
Weighted average dilutive stock options, restricted stock units and performance share units (in shares)	501,000	828,000	1,628,000
Assumed conversion of Convertible Senior Notes (in shares)	985,000	729,000	1,405,000
Weighted average number of diluted common and common equivalent shares outstanding (in shares)	51,326,000	51,211,000	50,988,000
Anti-dilutive potential common shares (in shares)				2,202,000	1,453,000	2,487,000	2,000,000	1,200,000	1,900,000
Aggregate principal amount										$ 172,500,000			$ 172,500,000
Debt Instrument Hedge Agreement Shares Purchaseable Shares											4,300,000
Debt Instrument, Convertible, Conversion Price											$ 40.38
Debt Instrument Hedge Agreement Shares Purchaseable By Counterparties Shares											4,300,000
Debt Instrument Hedge Agreement Effective Conversion Price											$ 50.47
Debt Instrument, Convertible, Number of Equity Instruments													4,300,000
Proceeds from Conversion Spread Hedge Financing Activities	$ 0		$ 42,984,000									$ 43,000,000