EMPLOYEE BENEFIT PLANS - FUNDED STATUS (DETAILS) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Qualified Defined Benefit [Member]
Benefit obligation
Beginning of year	$ 1,343.0	$ 1,179.8
Service cost	35.3	32.3	44.2
Interest cost	72.9	67.7	66.9
Plan amendments	(21.6)	0
Actuarial (gain) loss	206.3	101.0
Benefits paid	(41.6)	(37.8)
End of year	1,594.3	1,343.0	1,179.8
Accumulated benefit obligation	1,483.0	1,232.1
Plan assets at fair value
Beginning of year	1,142.7	906.9
Actual return on plan assets	53.6	128.0
Employer contributions	133.3	145.6
Benefits paid	(41.6)	(37.8)
End of year	1,288.0	1,142.7	906.9
Funded status (unfunded)	(306.3)	(200.3)
Percent funded	81.00%	85.00%
Qualified defined benefit, Contributions Due to Allocation Requirements [Member]
Plan assets at fair value
Employer contributions	100.0	100.0
Nonqualified Defined Benefit [Member]
Benefit obligation
Beginning of year	41.1	37.3
Service cost	1.0	0.8	0.7
Interest cost	2.2	2.1	2.2
Plan amendments	0.2	0
Actuarial (gain) loss	3.2	4.1
Benefits paid	(4.9)	(3.2)
End of year	42.8	41.1	37.3
Accumulated benefit obligation	41.8	40.4
Plan assets at fair value
Beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	4.9	3.2
Benefits paid	(4.9)	(3.2)
End of year	0	0	0
Funded status (unfunded)	(42.8)	(41.1)
Postretirement Medical Benefits [Member]
Benefit obligation
Beginning of year	132.5	117.3
Service cost	6.0	5.3	5.6
Interest cost	7.2	6.7	7.8
Actuarial (gain) loss	(22.9)	4.9
Benefits paid	(2.6)	(1.7)
End of year	120.2	132.5	117.3
Plan assets at fair value
Beginning of year	0	0
Employer contributions	2.6	1.7
Benefits paid	(2.6)	(1.7)
End of year	0	0	0
Funded status (unfunded)	$ (120.2)	$ (132.5)