EMPLOYEE BENEFIT PLANS - NET PENSION EXPENSE (DETAILS) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Qualified Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 9.6	$ 9.0
Interest cost	18.2	18.3
Expected return on assets	(23.3)	(22.1)
Amortization of prior service cost	(0.2)	(0.2)
Recognized actuarial loss	9.9	6.1
Net pension expense	14.2	11.1
Nonqualified Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0.2	0.2
Interest cost	0.5	0.6
Expected return on assets	0	0
Amortization of prior service cost	0	0
Recognized actuarial loss	0.2	0.1
Net pension expense	0.9	0.9
Postretirement Medical Benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	1.2	1.5
Interest cost	1.4	1.8
Expected return on assets	0	0
Amortization of prior service cost	0.1	0.1
Recognized actuarial loss	(0.1)	0.3
Net pension expense	$ 2.6	$ 3.7