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
Revenues
Total revenues	$ 867,720	$ 886,355	$ 2,536,848	$ 2,391,307
Expenses
Total expenses	776,018	791,865	2,289,924	2,169,781
Operating income (loss)
Total operating income	91,702	94,490	246,924	221,526
Interest expense-other than on deposit liabilities and other bank borrowings	(20,020)	(19,949)	(58,758)	(64,266)
Allowance for borrowed funds used during construction	688	658	2,451	1,731
Allowance for equity funds used during construction	1,611	1,570	5,548	4,131
Income before income taxes	73,981	76,769	196,165	163,122
Income taxes	25,804	27,894	69,926	57,700
Net income	48,177	48,875	126,239	105,422
Preferred stock dividends of subsidiaries	471	471	1,417	1,417
Net income for common stock	47,706	48,404	124,822	104,005
Basic earnings per common share (in dollars per share)	$ 0.49	$ 0.50	$ 1.29	$ 1.09
Diluted earnings per common share (in dollars per share)	$ 0.49	$ 0.50	$ 1.29	$ 1.09
Dividends per common share (in dollars per share)	$ 0.31	$ 0.31	$ 0.93	$ 0.93
Weighted-average number of common shares outstanding (in shares)	97,157	95,873	96,674	95,365
Dilutive effect of share-based compensation (in shares)	361	227	423	306
Adjusted weighted-average shares (in shares)	97,518	96,100	97,097	95,671
Electric utility
Revenues
Total revenues	801,095	820,254	2,340,257	2,194,327
Expenses
Total expenses	726,276	745,298	2,146,688	2,031,645
Operating income (loss)
Total operating income	74,819	74,956	193,569	162,682
Income before income taxes	61,268	62,244	154,976	122,114
Income taxes	22,395	23,787	58,429	46,446
Net income	38,873	38,457	96,547	75,668
Preferred stock dividends of subsidiaries	498	498	1,496	1,496
Net income for common stock	38,375	37,959	95,051	74,172
Bank
Revenues
Total revenues	66,596	66,100	196,569	197,731
Expenses
Total expenses	44,974	42,931	130,161	128,988
Operating income (loss)
Total operating income	21,622	23,169	66,408	68,743
Income before income taxes	21,627	23,166	66,964	68,699
Income taxes	7,419	7,709	22,690	24,196
Net income	14,208	15,457	44,274	44,503
Net income for common stock	14,208	15,457	44,274	44,503
Other
Revenues
Total revenues	29	1	22	(751)
Expenses
Total expenses	4,768	3,636	13,075	9,148
Operating income (loss)
Total operating income	(4,739)	(3,635)	(13,053)	(9,899)
Income before income taxes	(8,914)	(8,641)	(25,775)	(27,691)
Income taxes	(4,010)	(3,602)	(11,193)	(12,942)
Net income	(4,904)	(5,039)	(14,582)	(14,749)
Preferred stock dividends of subsidiaries	(27)	(27)	(79)	(79)
Net income for common stock	$ (4,877)	$ (5,012)	$ (14,503)	$ (14,670)