SEGMENT INFORMATION (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Operating Revenues	$ 1,892,590,000	$ 1,861,529,000	$ 5,523,475,000	$ 4,589,835,000
Operating Income	399,262,000	412,905,000	1,168,783,000	786,813,000
Total Interest Expense	(87,476,000)	(90,361,000)	(250,583,000)	(245,856,000)
Income Tax Expense	(109,351,000)	(117,360,000)	(325,442,000)	(199,379,000)
Net Income	211,380,000	209,508,000	614,413,000	356,482,000
Net Income Attributable to Noncontrolling Interests	(1,879,000)	(1,880,000)	(5,803,000)	(5,253,000)
Net Income Attributable to Controlling Interests	209,501,000	207,628,000	608,610,000	351,229,000
Total Assets	28,444,318,000		28,444,318,000		28,302,824,000
Investments in Property, Plant and Equipment			1,073,759,000	1,081,750,000
Electric Distribution Member
Segment Reporting Information [Line Items]
Operating Revenues	1,508,600,000	1,483,700,000	4,104,400,000	3,499,700,000
Depreciation And Amortization	(159,600,000)	(172,600,000)	(488,700,000)	(398,100,000)
Operating Expenses, Other	(1,064,100,000)	(1,027,400,000)	(2,952,400,000)	(2,654,400,000)
Operating Income	284,900,000	283,700,000	663,300,000	447,200,000
Net Income Attributable to Controlling Interests	156,900,000	150,500,000	347,500,000	212,100,000
Total Assets	17,912,900,000		17,912,900,000		18,047,300,000
Investments in Property, Plant and Equipment			501,900,000	461,300,000
Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Operating Revenues	97,100,000	91,300,000	613,000,000	361,500,000
Depreciation And Amortization	(16,400,000)	(12,600,000)	(50,500,000)	(32,700,000)
Operating Expenses, Other	(89,400,000)	(77,200,000)	(483,600,000)	(292,900,000)
Operating Income	(8,700,000)	1,500,000	78,900,000	35,900,000
Net Income Attributable to Controlling Interests	(10,400,000)	(4,400,000)	34,100,000	8,300,000
Total Assets	2,656,800,000		2,656,800,000		2,717,400,000
Investments in Property, Plant and Equipment			91,200,000	105,900,000
Transmission [Member]
Segment Reporting Information [Line Items]
Operating Revenues	234,100,000	235,600,000	721,500,000	627,200,000
Depreciation And Amortization	(34,500,000)	(29,700,000)	(100,900,000)	(79,500,000)
Operating Expenses, Other	(73,400,000)	(66,300,000)	(199,100,000)	(179,500,000)
Operating Income	126,200,000	139,600,000	421,500,000	368,200,000
Net Income Attributable to Controlling Interests	58,600,000	71,100,000	215,400,000	181,100,000
Total Assets	6,566,100,000		6,566,100,000		6,187,700,000
Investments in Property, Plant and Equipment			458,200,000	476,000,000
Other Segment [Member]
Segment Reporting Information [Line Items]
Operating Revenues	212,500,000	219,500,000	650,400,000	582,900,000
Depreciation And Amortization	(11,200,000)	(17,500,000)	(52,000,000)	(39,100,000)
Operating Expenses, Other	(206,800,000)	(216,800,000)	(599,000,000)	(614,500,000)
Operating Income	(5,500,000)	(14,800,000)	(600,000)	(70,700,000)
Net Income Attributable to Controlling Interests	313,100,000	313,900,000	868,700,000	511,600,000
Total Assets	19,446,900,000		19,446,900,000		18,832,600,000
Investments in Property, Plant and Equipment			22,500,000	38,600,000
Eliminations Segment [Member]
Segment Reporting Information [Line Items]
Operating Revenues	(159,700,000)	(168,600,000)	(565,800,000)	(481,500,000)
Depreciation And Amortization	2,600,000	1,100,000	7,200,000	2,600,000
Operating Expenses, Other	159,500,000	170,400,000	564,300,000	485,100,000
Operating Income	2,400,000	2,900,000	5,700,000	6,200,000
Net Income Attributable to Controlling Interests	(308,700,000)	(323,500,000)	(857,100,000)	(561,900,000)
Total Assets	(18,138,400,000)		(18,138,400,000)		(17,482,200,000)
Investments in Property, Plant and Equipment			0	0
Total [Member]
Segment Reporting Information [Line Items]
Operating Revenues	1,892,600,000	1,861,500,000	5,523,500,000	4,589,800,000
Depreciation And Amortization	(219,100,000)	(231,300,000)	(684,900,000)	(546,800,000)
Operating Expenses, Other	(1,274,200,000)	(1,217,300,000)	(3,669,800,000)	(3,256,200,000)
Operating Income	399,300,000	412,900,000	1,168,800,000	786,800,000
Net Income Attributable to Controlling Interests	209,500,000	207,600,000	608,600,000	351,200,000
Total Assets	28,444,300,000		28,444,300,000		28,302,800,000
Investments in Property, Plant and Equipment			$ 1,073,800,000	$ 1,081,800,000