DEBT (Details) (USD $)			3 Months Ended			3 Months Ended		3 Months Ended		3 Months Ended		3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012 Senior notes 5.875% due 1/15/12 [Member]	Mar. 31, 2013 Senior notes 6.30% Due 8/15/14 [Member]	Dec. 31, 2012 Senior notes 6.30% Due 8/15/14 [Member]	Mar. 31, 2013 Senior notes 6.125% due 1/15/15 [Member]	Dec. 31, 2012 Senior notes 6.125% due 1/15/15 [Member]	Mar. 31, 2013 Senior notes 5.95% due 3/15/17 [Member]	Dec. 31, 2012 Senior notes 5.95% due 3/15/17 [Member]	Mar. 31, 2013 Senior notes 5.45% Due 6/7/21 [Member]	Dec. 31, 2012 Senior notes 5.45% Due 6/7/21 [Member]	Mar. 31, 2013 Revolving Credit Due 2016 [Member] Y	Dec. 31, 2012 Revolving Credit Due 2016 [Member]
Debt Instrument [Line Items]
Total debt, including current portion	$ 1,585,312,000	$ 1,585,190,000		$ 374,775,000	$ 374,718,000	$ 228,845,000	$ 228,845,000	$ 382,674,000	$ 382,639,000	$ 599,018,000	$ 598,988,000	$ 0	$ 0
Stated interest rate			5.875%	6.30%		6.125%		5.95%		5.45%
Unamortized discount				322,000				561,000		982,000
Less current portion of total debt	0	0
Total long-term debt	1,585,312,000	1,585,190,000
Repayment of Senior Notes			233,900,000
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
Maturity Date				Aug. 15, 2014		Jan. 15, 2015		Mar. 15, 2017		Jun. 07, 2021