EMPLOYEE BENEFIT PLANS - NET PENSION EXPENSE (DETAILS) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Qualified Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 9.6	$ 8.7	$ 28.7	$ 26.7
Interest cost	18.2	18.1	54.7	54.7
Expected return on assets	(23.2)	(22.0)	(69.7)	(66.2)
Amortization of prior service cost	(0.2)	(0.3)	(0.7)	(0.7)
Curtailment loss	0	0	0	0
Recognized actuarial loss	9.9	5.5	29.7	17.7
Net pension expense	14.3	10.0	42.7	32.2
Nonqualified Defined Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0.3	0.3	0.7	0.7
Interest cost	0.4	0.6	1.4	1.7
Expected return on assets	0	0	0	0
Amortization of prior service cost	0	0	0	0
Curtailment loss	0	0.2	0	0.2
Recognized actuarial loss	0.2	0.1	0.6	0.4
Net pension expense	0.9	1.2	2.7	3.0
Postretirement Medical Benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	1.2	1.5	3.7	4.5
Interest cost	1.4	1.8	4.1	5.4
Expected return on assets	0	0	0	0
Amortization of prior service cost	0.1	0	0.4	0.2
Curtailment loss	0	0	0	0
Recognized actuarial loss	(0.1)	0.3	(0.4)	0.9
Net pension expense	$ 2.6	$ 3.6	$ 7.8	$ 11.0