EMPLOYEE BENEFIT PLANS - NET PENSION EXPENSE (DETAILS) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Qualified Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 9.5	$ 9.0	$ 19.1	$ 18.0
Interest cost	18.3	18.3	36.5	36.6
Expected return on assets	(23.2)	(22.1)	(46.5)	(44.2)
Amortization of prior service cost	(0.3)	(0.2)	(0.5)	(0.4)
Recognized actuarial loss	9.9	6.1	19.8	12.2
Net pension expense	14.2	11.1	28.4	22.2
Nonqualified Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0.2	0.2	0.4	0.4
Interest cost	0.5	0.5	1.0	1.1
Expected return on assets	0	0	0	0
Amortization of prior service cost	0	0	0	0
Recognized actuarial loss	0.2	0.2	0.4	0.3
Net pension expense	0.9	0.9	1.8	1.8
Postretirement Medical Benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	1.3	1.5	2.5	3.0
Interest cost	1.3	1.8	2.7	3.6
Expected return on assets	0	0	0	0
Amortization of prior service cost	0.2	0.1	0.3	0.2
Recognized actuarial loss	(0.2)	0.3	(0.3)	0.6
Net pension expense	$ 2.6	$ 3.7	$ 5.2	$ 7.4