CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CONSOLIDATED STATEMENTS OF INCOME
OPERATING REVENUES	$ 3,454,628	$ 3,301,804	$ 3,241,379
OPERATING EXPENSES
Fuel and purchased power	1,095,709	994,790	1,009,464
Operations and maintenance	924,727	884,769	904,286
Depreciation and amortization	415,708	404,336	427,054
Taxes other than income taxes	164,167	159,323	147,408
Other expenses	7,994	6,831	6,659
Total	2,608,305	2,450,049	2,494,871
OPERATING INCOME	846,323	851,755	746,508
OTHER INCOME (DEDUCTIONS)
Allowance for equity funds used during construction (Note 1)	25,581	22,436	23,707
Other income (Note 18)	1,704	1,606	3,111
Other expense (Note 18)	(16,024)	(19,842)	(10,451)
Total	11,261	4,200	16,367
INTEREST EXPENSE
Interest charges	201,888	214,616	241,995
Allowance for borrowed funds used during construction (Note 1)	(14,861)	(14,971)	(18,358)
Total	187,027	199,645	223,637
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	670,557	656,310	539,238
INCOME TAXES (Note 4)	230,591	237,317	183,604
INCOME FROM CONTINUING OPERATIONS	439,966	418,993	355,634
INCOME (LOSS) FROM DISCONTINUED OPERATIONS
Net of income tax expense (benefit) of $--, $(3,813) and $7,418 (Note 1)		(5,829)	11,306
NET INCOME	439,966	413,164	366,940
Less: Net income attributable to noncontrolling interests (Note 19)	33,892	31,622	27,467
NET INCOME ATTRIBUTABLE TO COMMON SHAREHOLDERS	406,074	381,542	339,473
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING - BASIC (in shares)	109,984	109,510	109,053
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING - DILUTED (in shares)	110,806	110,527	109,864
EARNINGS PER WEIGHTED - AVERAGE COMMON SHARE OUTSTANDING
Income from continuing operations attributable to common shareholders - basic (in dollars per share)	$ 3.69	$ 3.54	$ 3.01
Net income attributable to common shareholders - basic (in dollars per share)	$ 3.69	$ 3.48	$ 3.11
Income from continuing operations attributable to common shareholders - diluted (in dollars per share)	$ 3.66	$ 3.50	$ 2.99
Net income attributable to common shareholders - diluted (in dollars per share)	$ 3.66	$ 3.45	$ 3.09
AMOUNTS ATTRIBUTABLE TO COMMON SHAREHOLDERS:
Income from continuing operations, net of tax	406,074	387,380	328,110
Discontinued operations, net of tax		(5,838)	11,363
Net income attributable to common shareholders	$ 406,074	$ 381,542	$ 339,473