CONDENSED CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
OPERATING REVENUES	$ 1,109,475	$ 1,124,841	$ 2,608,682	$ 2,573,487
OPERATING EXPENSES
Fuel and purchased power	302,894	337,896	783,926	793,952
Operations and maintenance	220,729	210,035	647,628	675,654
Depreciation and amortization	100,353	106,350	301,068	319,550
Taxes other than income taxes	36,507	34,223	120,271	112,002
Other expenses	1,022	1,320	5,323	4,536
Total	661,505	689,824	1,858,216	1,905,694
OPERATING INCOME	447,970	435,017	750,466	667,793
OTHER INCOME (DEDUCTIONS)
Allowance for equity funds used during construction	5,708	7,378	15,639	18,697
Other income (Note 11)	420	441	1,357	2,630
Other expense (Note 11)	(5,696)	(3,052)	(12,433)	(7,921)
Total	432	4,767	4,563	13,406
INTEREST EXPENSE
Interest charges	52,242	62,034	162,209	183,251
Allowance for borrowed funds used during construction	(3,830)	(6,939)	(10,428)	(14,371)
Total	48,412	55,095	151,781	168,880
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	399,990	384,689	603,248	512,319
INCOME TAXES	147,116	131,416	219,160	176,229
INCOME FROM CONTINUING OPERATIONS	252,874	253,273	384,088	336,090
INCOME (LOSS) FROM DISCONTINUED OPERATIONS
Net of income tax expense (benefit) of $(7) and $6,216 for three months ended September 30, 2012 and 2011 and $(1,047) and $7,121 for nine months ended September 30, 2012 and 2011 (Note 13)	(11)	9,512	(1,595)	10,860
NET INCOME	252,863	262,785	382,493	346,950
Less: Net income attributable to noncontrolling interests (Note 7)	8,040	7,426	23,582	20,041
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	244,823	255,359	358,911	326,909
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING - BASIC (in shares)	109,555	109,128	109,449	109,003
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING - DILUTED (in shares)	110,655	109,861	110,420	109,683
EARNINGS PER WEIGHTED-AVERAGE COMMON SHARE OUTSTANDING
Income from continuing operations attributable to common shareholders - basic (in dollars per share)	$ 2.23	$ 2.25	$ 3.29	$ 2.90
Net income attributable to common shareholders - basic (in dollars per share)	$ 2.23	$ 2.34	$ 3.28	$ 3.00
Income from continuing operations attributable to common shareholders - diluted (in dollars per share)	$ 2.21	$ 2.24	$ 3.26	$ 2.88
Net income attributable to common shareholders - diluted (in dollars per share)	$ 2.21	$ 2.32	$ 3.25	$ 2.98
DIVIDENDS DECLARED PER SHARE (in dollars per share)			$ 1.575	$ 1.575
AMOUNTS ATTRIBUTABLE TO COMMON SHAREHOLDERS:
Income from continuing operations, net of tax	244,834	245,838	360,515	316,001
Discontinued operations, net of tax	(11)	9,521	(1,604)	10,908
Net income attributable to common shareholders	$ 244,823	$ 255,359	$ 358,911	$ 326,909