LONG-TERM DEBT (Details) (USD $)	6 Months Ended		1 Months Ended			6 Months Ended	1 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Revolving Credit Agreement 2011	Jun. 30, 2013 4.150% Notes due July 1, 2023	Jul. 31, 2013 4.625% Notes due July 15, 2013 Subsequent Event	Jun. 30, 2013 4.150% Notes	Jun. 30, 2013 4.150% Notes	Jul. 31, 2013 4.150% Notes Subsequent Event
Debt Instrument
Notes issued					$ 500,000,000	$ 500,000,000
Notes payable, interest rate				4.625%	4.15%	4.15%
Public offering price as a percentage of par			99.81%
Financing costs	3,250,000				3,300,000
Proceeds from offering, net					495,800,000
Line of Credit, maximum borrowing capacity		1,250,000,000
Credit facility, additional borrowing capacity		612,700,000
Principal amount of debt repaid				300,000,000			300,000,000
Accrued interest repaid				6,900,000
Derivatives settled	$ 62,009,000					$ 62,000,000