EMPLOYEE BENEFIT PLANS (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Benefits
Net regulatory assets
Net actuarial losses	$ 34.6
Prior service costs (credits)	0.6
Total 2014 - estimated amortization	35.2
Components of net periodic benefit cost (including amounts capitalized to the balance sheets)
Service cost	30.2	46.0	41.4
Interest cost	71.2	78.0	80.1
Expected return on plan assets	(105.5)	(107.9)	(100.0)
Amortization of transition obligation	0	0	0
Amortization of prior service cost (credit)	4.0	5.0	5.3
Amortization of net actuarial loss	56.7	34.0	18.1
Net periodic benefit cost	56.6	55.1	44.9
Pension Benefits | Nonregulated segments
Accumulated other comprehensive loss (pre-tax)
Net actuarial loss	33.3	59.1
Prior service costs (credits)	0	0.2
Total	33.3	59.3
Pension Benefits | Utility segments
Net regulatory assets
Net actuarial loss	399.3	683.1
Prior service costs (credits)	2.4	6.2
Total	401.7	689.3
Other Benefits
Net regulatory assets
Net actuarial losses	2.5
Prior service costs (credits)	(2.4)
Total 2014 - estimated amortization	0.1
Components of net periodic benefit cost (including amounts capitalized to the balance sheets)
Service cost	24.9	20.8	19.0
Interest cost	24.8	28.5	29.5
Expected return on plan assets	(30.6)	(28.2)	(21.4)
Amortization of transition obligation	0	0.3	0.3
Amortization of prior service cost (credit)	(2.5)	(3.4)	(3.9)
Amortization of net actuarial loss	8.4	6.6	4.0
Net periodic benefit cost	25.0	24.6	27.5
Other Benefits | Nonregulated segments
Accumulated other comprehensive loss (pre-tax)
Net actuarial loss	0.7	1.3
Prior service costs (credits)	(0.2)	(0.6)
Total	0.5	0.7
Other Benefits | Utility segments
Net regulatory assets
Net actuarial loss	8.9	117.3
Prior service costs (credits)	(12.0)	(14.3)
Total	$ (3.1)	$ 103.0