DEBT (Details) (USD $)	6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Total debt, including current portion	$ 1,584,945,000	$ 1,818,603,000
Less current portion of total debt	0	233,903,000
Total long-term debt	1,584,945,000	1,584,700,000
Senior notes 5.875% due 1/15/12 [Member]
Debt Instrument [Line Items]
Total debt, including current portion	0	233,903,000
Stated interest rate	5.875%
Maturity date	Jan. 15, 2012
Repayment of Senior Notes	233,900,000
Senior notes 6.30% Due 8/15/14 [Member]
Debt Instrument [Line Items]
Total debt, including current portion	374,605,000	374,490,000
Stated interest rate	6.30%
Maturity date	Aug. 15, 2014
Unamortized discount	492,000
Senior notes 6.125% due 1/15/15 [Member]
Debt Instrument [Line Items]
Total debt, including current portion	228,845,000	228,845,000
Stated interest rate	6.125%
Maturity date	Jan. 15, 2015
Senior notes 5.95% due 3/15/17 [Member]
Debt Instrument [Line Items]
Total debt, including current portion	382,567,000	382,497,000
Stated interest rate	5.95%
Maturity date	Mar. 15, 2017
Unamortized discount	668,000
Senior notes 5.45% Due 6/7/21 [Member]
Debt Instrument [Line Items]
Total debt, including current portion	598,928,000	598,868,000
Stated interest rate	5.45%
Maturity date	Jun. 07, 2021
Unamortized discount	1,072,000
Revolving Credit Due 2016 [Member]
Debt Instrument [Line Items]
Total debt, including current portion	0	0
Term of revolving credit facility (in years)	5
Unsecured revolving credit agreement	750,000,000
Maximum borrowing capacity under revolving credit faclity if optional increase requested	$ 1,000,000,000
Leverage ratio required under debt covenants	3 to 1