CONDENSED CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
OPERATING REVENUES	$ 878,576	$ 799,799	$ 1,499,207	$ 1,448,646
OPERATING EXPENSES
Fuel and purchased power	264,723	244,049	481,032	456,056
Operations and maintenance	216,236	210,590	426,899	465,619
Depreciation and amortization	100,606	106,617	200,715	213,200
Taxes other than income taxes	41,289	40,155	83,764	77,779
Other expenses	1,233	1,396	4,301	3,216
Total	624,087	602,807	1,196,711	1,215,870
OPERATING INCOME	254,489	196,992	302,496	232,776
OTHER INCOME (DEDUCTIONS)
Allowance for equity funds used during construction	5,175	5,924	9,931	11,319
Other income (Note 11)	177	557	937	2,247
Other expense (Note 11)	(2,669)	(3,186)	(6,737)	(4,927)
Total	2,683	3,295	4,131	8,639
INTEREST EXPENSE
Interest charges	53,000	60,140	109,967	121,217
Allowance for borrowed funds used during construction	(3,447)	(3,856)	(6,598)	(7,432)
Total	49,553	56,284	103,369	113,785
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	207,619	144,003	203,258	127,630
INCOME TAXES	76,689	50,818	72,044	44,813
INCOME FROM CONTINUING OPERATIONS	130,930	93,185	131,214	82,817
INCOME (LOSS) FROM DISCONTINUED OPERATIONS
Net of income tax expense (benefit) of $(535) and $773 for three months ended June 30, 2012 and 2011 and $(1,040) and $906 for six months ended June 30, 2012 and 2011 (Note 13)	(819)	654	(1,584)	1,348
NET INCOME	130,111	93,839	129,630	84,165
Less: Net income attributable to noncontrolling interests (Note 7)	7,766	7,154	15,542	12,615
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	122,345	86,685	114,088	71,550
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING - BASIC (in shares)	109,491	109,044	109,395	108,939
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING - DILUTED (in shares)	110,359	109,718	110,183	109,540
EARNINGS PER WEIGHTED-AVERAGE COMMON SHARE OUTSTANDING
Income from continuing operations attributable to common shareholders - basic (in dollars per share)	$ 1.12	$ 0.79	$ 1.06	$ 0.64
Net income attributable to common shareholders - basic (in dollars per share)	$ 1.12	$ 0.80	$ 1.04	$ 0.66
Income from continuing operations attributable to common shareholders - diluted (in dollars per share)	$ 1.12	$ 0.78	$ 1.05	$ 0.64
Net income attributable to common shareholders - diluted (in dollars per share)	$ 1.11	$ 0.79	$ 1.04	$ 0.65
DIVIDENDS DECLARED PER SHARE (in dollars per share)	$ 1.05	$ 1.05	$ 1.575	$ 1.575
AMOUNTS ATTRIBUTABLE TO COMMON SHAREHOLDERS:
Income from continuing operations, net of tax	123,164	86,001	115,681	70,163
Discontinued operations, net of tax	(819)	684	(1,593)	1,387
Net income attributable to common shareholders	$ 122,345	$ 86,685	$ 114,088	$ 71,550