CREDIT FACILITIES AND LONG-TERM DEBT (Details) (USD $) In Millions, unless otherwise specified					3 Months Ended		6 Months Ended			1 Months Ended		1 Months Ended			1 Months Ended				1 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 Senior Credit Facility due 2011 and 2016	Dec. 31, 2010 Senior Credit Facility due 2011 and 2016	Jun. 30, 2011 Senior Credit Facility due 2011	Jun. 30, 2010 Senior Credit Facility due 2011	Jun. 30, 2011 Senior Credit Facility due 2011	Jun. 30, 2010 Senior Credit Facility due 2011	Dec. 31, 2010 Senior Credit Facility due 2011	Jun. 30, 2011 Senior term loan	Dec. 31, 2010 Senior term loan	Jul. 31, 2011 Senior revolving credit facility	Jun. 30, 2011 Senior revolving credit facility	Dec. 31, 2010 Senior revolving credit facility	Jun. 30, 2011 4.65% Senior Notes due 2021	Dec. 31, 2010 4.65% Senior Notes due 2021	Jun. 30, 2011 6.89% Series C Senior Notes due 2012	Dec. 31, 2010 6.89% Series C Senior Notes due 2012	Jun. 30, 2011 Bridge loan facility	May 31, 2011 Bridge loan facility	Jun. 17, 2011 Bridge loan facility	May 03, 2011 Bridge loan facility	Jun. 30, 2011 3.82% Series D Senior Notes due 2017	Dec. 31, 2010 3.82% Series D Senior Notes due 2017
Credit facility and long-term debt
Long-term debt	$ 693.9	$ 513.9	$ 314.0	$ 483.0									$ 14.0	$ 8.0	$ 349.4		$ 3.5	$ 3.9					$ 27.0	$ 27.0
Less: current portion of long-term debt	300.8	483.8
Noncurrent portion of long-term debt	393.1	30.1
Maximum borrowing capacity										300.0			250.0									400.0
Repayment on borrowing										175.0
Outstanding borrowing capacity										300.0	475.0											61.0
Debt interest rate (as a percent)															4.65%	4.65%	6.89%	6.89%			1.70%		3.82%	3.82%
Debt average interest rate (as a percent)					0.90%	0.90%	0.90%	0.90%
Debt average interest rate, after hedging activity (as a percent)					3.50%	4.20%	3.70%	4.20%
Debt average interest rate, before hedging activity (as a percent)					0.60%		0.60%		0.80%
Line of credit facility, additonal amount												500.0
Public debt offering															350.0
Debt offering term (in years)															10
Line of credit facility, term (in days)																				364
Line of credit facility, base rate												London Interbank Offered Rate (LIBOR)-based interest rate plus a margin								London Interbank Offered Rate (LIBOR) or the prime rate plus
Line of credit facility, repaid and cancelled																			$ 61.0