EQUITY METHOD INVESTMENTS (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income statement data
Earnings from equity method investments	$ 91.5	$ 87.2	$ 79.4
ATC, INDU Solar Holdings, LLC, and WRPC
Income statement data
Revenues	642.0	618.3	575.5
Operating expenses	306.2	292.1	269.6
Other expense	83.7	85.1	81.5
Net income	252.1	241.1	224.4
Earnings from equity method investments	91.4	87.2	79.4
Balance sheet data
Current assets	90.2	81.1
Noncurrent assets	3,587.2	3,347.4
Total assets	3,677.4	3,428.5
Current liabilities	383.6	253.0
Long-term debt	1,559.1	1,559.5
Other noncurrent liabilities	134.4	103.5
Shareholders' equity	1,600.3	1,512.5
Total liabilities and shareholders' equity	$ 3,677.4	$ 3,428.5