EMPLOYEE BENEFIT PLANS (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Plan	Dec. 31, 2010	Dec. 31, 2009
Amounts recognized on the entity's Balance Sheets related to the funded status of the benefit plans
Noncurrent liabilities	$ 749.3	$ 603.4
Pension Benefits
Employee Benefit Plans
Number of non-contributory qualified pension plans covering substantially all employees	1
Change in benefit obligation
Obligation at the beginning of the period	1,418.5	1,337.4
Service cost	41.4	40.1	38.9
Interest cost	80.1	80.0	80.9
Actuarial loss, net	111.7	98.4
Benefit payments	(88.6)	(137.4)
Obligation at the end of the period	1,563.1	1,418.5	1,337.4
Change in fair value of plan assets
Fair value of plan assets at the beginning of the period	1,081.3	933.6
Actual return on plan assets	16.5	119.1
Employer contributions	90.3	166.0
Benefit payments	(88.6)	(137.4)
Fair value of plan assets at the end of the period	1,099.5	1,081.3	933.6
Amounts recognized on the entity's Balance Sheets related to the funded status of the benefit plans
Current liabilities	5.3	5.8
Noncurrent liabilities	458.3	331.4
Total liabilities	463.6	337.2
Information for pension plans with an accumulated benefit obligation in excess of plan assets
Projected benefit obligation	1,563.1	1,418.5
Accumulated benefit obligation	1,388.0	1,225.9
Fair value of plan assets	1,099.5	1,081.3
Funded status at the end of the period	(463.6)	(337.2)
Other Benefits
Change in benefit obligation
Obligation at the beginning of the period	538.5	475.5
Service cost	19.0	16.3	14.3
Interest cost	29.5	27.5	26.5
Plan amendments	(0.8)
Actuarial loss, net	9.2	41.1
Participant contributions	10.6	10.7
Benefit payments	(31.8)	(34.9)
Federal subsidy on benefits paid	2.6	2.3
Obligation at the end of the period	576.8	538.5	475.5
Change in fair value of plan assets
Fair value of plan assets at the beginning of the period	266.2	230.8
Actual return on plan assets	(1.0)	23.8
Employer contributions	41.2	35.8
Participant contributions	10.6	10.7
Benefit payments	(31.8)	(34.9)
Fair value of plan assets at the end of the period	285.5	266.2	230.8
Amounts recognized on the entity's Balance Sheets related to the funded status of the benefit plans
Current liabilities	0.3	0.3
Noncurrent liabilities	291.0	272.0
Total liabilities	291.3	272.3
Information for pension plans with an accumulated benefit obligation in excess of plan assets
Funded status at the end of the period	$ (291.3)	$ (272.3)