Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenues
Total revenues	$ 831,229	$ 867,720	$ 2,412,023	$ 2,536,848
Expenses
Total expenses	741,130	776,018	2,168,897	2,289,924
Operating income (loss)
Total operating income	90,099	91,702	243,126	246,924
Interest expense-other than on deposit liabilities and other bank borrowings	(20,304)	(20,020)	(59,705)	(58,758)
Allowance for borrowed funds used during construction	498	688	1,626	2,451
Allowance for equity funds used during construction	1,255	1,611	4,030	5,548
Income before income taxes	71,548	73,981	189,077	196,165
Income taxes	22,841	25,804	65,157	69,926
Net income	48,707	48,177	123,920	126,239
Preferred stock dividends of subsidiaries	471	471	1,417	1,417
Net income for common stock	48,236	47,706	122,503	124,822
Basic earnings per common share (in dollars per share)	$ 0.49	$ 0.49	$ 1.24	$ 1.29
Diluted earnings per common share (in dollars per share)	$ 0.48	$ 0.49	$ 1.23	$ 1.29
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)	99,204	97,157	98,670	96,674
Net effect of potentially dilutive shares (in shares)	614	361	620	423
Adjusted weighted-average shares (in shares)	99,818	97,518	99,290	97,097
Electric utility
Revenues
Total revenues	766,115	801,095	2,216,076	2,340,257
Expenses
Total expenses	694,201	726,276	2,030,071	2,146,688
Operating income (loss)
Total operating income	71,914	74,819	186,005	193,569
Income before income taxes	57,373	61,268	144,212	154,976
Income taxes	19,058	22,395	51,777	58,429
Net income	38,315	38,873	92,435	96,547
Preferred stock dividends of subsidiaries	498	498	1,496	1,496
Net income for common stock	37,817	38,375	90,939	95,051
Bank
Revenues
Total revenues	65,058	66,596	195,841	196,569
Expenses
Total expenses	42,223	44,974	126,550	130,161
Operating income (loss)
Total operating income	22,835	21,622	69,291	66,408
Income before income taxes	22,808	21,627	69,265	66,964
Income taxes	7,532	7,419	23,915	22,690
Net income	15,276	14,208	45,350	44,274
Net income for common stock	15,276	14,208	45,350	44,274
Other
Revenues
Total revenues	56	29	106	22
Expenses
Total expenses	4,706	4,768	12,276	13,075
Operating income (loss)
Total operating income	(4,650)	(4,739)	(12,170)	(13,053)
Income before income taxes	(8,633)	(8,914)	(24,400)	(25,775)
Income taxes	(3,749)	(4,010)	(10,535)	(11,193)
Net income	(4,884)	(4,904)	(13,865)	(14,582)
Preferred stock dividends of subsidiaries	(27)	(27)	(79)	(79)
Net income for common stock	$ (4,857)	$ (4,877)	$ (13,786)	$ (14,503)