CREDIT FACILITIES AND LONG-TERM DEBT (Details) (USD $) In Millions, unless otherwise specified			12 Months Ended		1 Months Ended		12 Months Ended			1 Months Ended				1 Months Ended			1 Months Ended	12 Months Ended			1 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Senior Credit Facility due 2011 and 2016	Dec. 31, 2010 Senior Credit Facility due 2011 and 2016	Jul. 31, 2011 Senior term loan	Jun. 30, 2011 Senior term loan	Dec. 31, 2011 Senior term loan	Jul. 13, 2011 Senior term loan	Dec. 31, 2010 Senior term loan	Jul. 31, 2011 Senior revolving credit facility	Dec. 31, 2011 Senior revolving credit facility	Jul. 13, 2011 Senior revolving credit facility	Dec. 31, 2010 Senior revolving credit facility	Jul. 31, 2011 Senior revolving credit facility Maximum	Dec. 31, 2011 3.82% Series D Senior Notes due 2017	Dec. 31, 2010 3.82% Series D Senior Notes due 2017	Jun. 30, 2011 4.65% Senior Notes due 2021 Y	Dec. 31, 2011 4.65% Senior Notes due 2021	Dec. 31, 2011 6.89% Series C Senior Notes due 2012	Dec. 31, 2010 6.89% Series C Senior Notes due 2012	May 31, 2011 Bridge loan facility D	May 03, 2011 Bridge loan facility
Credit facility and long-term debt
Long-term debt	$ 742.5	$ 513.9	$ 363.0	$ 483.0					$ 475.0		$ 363.0		$ 8.0		$ 27.0	$ 27.0		$ 349.4	$ 3.1	$ 3.9
Less: current portion of long-term debt	3.1	483.8
Noncurrent portion of long-term debt	739.4	30.1
Maximum borrowing capacity								500.0				500.0										400.0
Maximum borrowing capacity before amendment												250.0
Repayment on borrowing						175.0	300.0
Option to increase borrowings on the credit facility														250.0
Remaining borrowing capacity											137.0
Debt interest rate (as a percent)															3.82%				6.89%
Debt interest rate (as a percent)																		4.65%			1.70%
Debt average interest rate (as a percent)			0.86%	0.91%
Debt average interest rate, after hedging activity (as a percent)			4.07%	4.30%
Debt interest rate, at period end, prior to hedging activities (as a percent)			1.65%	0.83%
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					LIBOR					LIBOR											LIBOR plus an applicable margin
Line of credit facility, repaid and cancelled																					$ 61.0