SEGMENT INFORMATION (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Operating Revenues	$ 2,290,590,000	$ 1,995,023,000
Operating Income	467,689,000	418,945,000
Total Interest Expense	(89,975,000)	(76,255,000)
Other Income/(Loss), Net	1,667,000	7,765,000
Income Tax Expense	(141,545,000)	(120,487,000)
Net Income	237,836,000	229,968,000
Net Income Attributable to Noncontrolling Interests	(1,879,000)	(1,879,000)
Net Income Attributable to Controlling Interests	235,957,000	228,089,000
Total Assets	28,096,870,000		27,795,537,000
Investments in Property, Plant and Equipment	348,691,000	388,950,000
Electric Distribution Member
Segment Reporting Information [Line Items]
Operating Revenues	1,585,900,000	1,374,200,000
Depreciation And Amortization	(148,800,000)	(177,000,000)
Operating Expenses, Other	(1,210,900,000)	(1,004,900,000)
Operating Income	226,200,000	192,300,000
Total Interest Expense	47,400,000	42,100,000
Other Income/(Loss), Net	1,400,000	4,800,000
Net Income Attributable to Controlling Interests	112,200,000	99,500,000
Total Assets	18,882,900,000		17,260,000,000
Investments in Property, Plant and Equipment	189,400,000	157,800,000
Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Operating Revenues	432,800,000	361,800,000
Depreciation And Amortization	(17,700,000)	(17,400,000)
Operating Expenses, Other	(321,400,000)	(267,200,000)
Operating Income	93,700,000	77,200,000
Total Interest Expense	8,500,000	7,400,000
Other Income/(Loss), Net	100,000	200,000
Net Income Attributable to Controlling Interests	52,100,000	43,300,000
Total Assets	2,846,700,000		2,759,700,000
Investments in Property, Plant and Equipment	28,900,000	31,200,000
Transmission [Member]
Segment Reporting Information [Line Items]
Operating Revenues	252,100,000	239,500,000
Depreciation And Amortization	(37,000,000)	(31,800,000)
Operating Expenses, Other	(66,400,000)	(62,200,000)
Operating Income	148,700,000	145,500,000
Total Interest Expense	25,500,000	21,900,000
Other Income/(Loss), Net	1,500,000	2,800,000
Net Income Attributable to Controlling Interests	74,900,000	79,900,000
Total Assets	5,165,600,000		6,745,800,000
Investments in Property, Plant and Equipment	112,200,000	185,400,000
Other Segment [Member]
Segment Reporting Information [Line Items]
Operating Revenues	172,200,000	217,200,000
Depreciation And Amortization	(7,000,000)	(19,000,000)
Operating Expenses, Other	(165,400,000)	(197,400,000)
Operating Income	(200,000)	800,000
Total Interest Expense	9,600,000	6,400,000
Other Income/(Loss), Net	294,800,000	321,900,000
Net Income Attributable to Controlling Interests	291,700,000	322,800,000
Total Assets	11,913,600,000		11,842,400,000
Investments in Property, Plant and Equipment	18,200,000	14,600,000
Eliminations Segment [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(152,400,000)	(197,700,000)
Depreciation And Amortization	1,800,000	1,700,000
Operating Expenses, Other	149,900,000	199,200,000
Operating Income	(700,000)	3,200,000
Total Interest Expense	(1,000,000)	(1,500,000)
Other Income/(Loss), Net	(296,100,000)	(321,900,000)
Net Income Attributable to Controlling Interests	(294,900,000)	(317,400,000)
Total Assets	(10,711,900,000)		(10,812,400,000)
Investments in Property, Plant and Equipment	0	0
Total [Member]
Segment Reporting Information [Line Items]
Operating Revenues	2,290,600,000	1,995,000,000
Depreciation And Amortization	(208,700,000)	(243,500,000)
Operating Expenses, Other	(1,614,200,000)	(1,332,500,000)
Operating Income	467,700,000	419,000,000
Total Interest Expense	90,000,000	76,300,000
Other Income/(Loss), Net	1,700,000	7,800,000
Net Income Attributable to Controlling Interests	236,000,000	228,100,000
Total Assets	28,096,900,000		27,795,500,000
Investments in Property, Plant and Equipment	$ 348,700,000	$ 389,000,000