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
Revenues
Total revenues	$ 854,268	$ 794,319	$ 1,669,128	$ 1,504,952
Expenses
Total expenses	774,862	730,658	1,513,906	1,377,916
Operating income (loss)
Total operating income	79,406	63,661	155,222	127,036
Interest expense-other than on deposit liabilities and other bank borrowings	(20,199)	(24,177)	(38,738)	(44,317)
Allowance for borrowed funds used during construction	893	553	1,763	1,073
Allowance for equity funds used during construction	1,997	1,317	3,937	2,561
Income before income taxes	62,097	41,354	122,184	86,353
Income taxes	22,824	13,742	44,122	29,806
Net income	39,273	27,612	78,062	56,547
Preferred stock dividends of subsidiaries	473	473	946	946
Net income for common stock	38,800	27,139	77,116	55,601
Basic earnings per common share (in dollars per share)	$ 0.40	$ 0.28	$ 0.80	$ 0.58
Diluted earnings per common share (in dollars per share)	$ 0.40	$ 0.28	$ 0.80	$ 0.58
Dividends per common share (in dollars per share)	$ 0.31	$ 0.31	$ 0.62	$ 0.62
Weighted-average number of common shares outstanding (in shares)	96,693	95,393	96,430	95,107
Dilutive effect of share-based compensation (in shares)	286	162	389	287
Adjusted weighted-average shares (in shares)	96,979	95,555	96,819	95,394
Electric utility
Revenues
Total revenues	789,552	728,738	1,539,162	1,374,073
Expenses
Total expenses	728,056	686,220	1,420,412	1,286,347
Operating income (loss)
Total operating income	61,496	42,518	118,750	87,726
Income before income taxes	48,501	28,603	93,708	59,870
Income taxes	18,626	11,080	36,034	22,659
Net income	29,875	17,523	57,674	37,211
Preferred stock dividends of subsidiaries	499	499	998	998
Net income for common stock	29,376	17,024	56,676	36,213
Bank
Revenues
Total revenues	64,721	66,318	129,973	131,631
Expenses
Total expenses	42,847	42,498	85,187	86,057
Operating income (loss)
Total operating income	21,874	23,820	44,786	45,574
Income before income taxes	21,873	23,806	45,337	45,533
Income taxes	7,684	8,611	15,271	16,487
Net income	14,189	15,195	30,066	29,046
Net income for common stock	14,189	15,195	30,066	29,046
Other
Revenues
Total revenues	(5)	(737)	(7)	(752)
Expenses
Total expenses	3,959	1,940	8,307	5,512
Operating income (loss)
Total operating income	(3,964)	(2,677)	(8,314)	(6,264)
Income before income taxes	(8,277)	(11,055)	(16,861)	(19,050)
Income taxes	(3,486)	(5,949)	(7,183)	(9,340)
Net income	(4,791)	(5,106)	(9,678)	(9,710)
Preferred stock dividends of subsidiaries	(26)	(26)	(52)	(52)
Net income for common stock	$ (4,765)	$ (5,080)	$ (9,626)	$ (9,658)