Consolidated Statements of Income (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenues
Total revenues	$ 717,176	$ 867,096	$ 1,978,950	$ 2,449,502
Expenses
Total expenses	620,081	775,060	1,739,619	2,185,069
Operating income (loss)
Total operating income	97,095	92,036	239,331	264,433
Interest expense, net—other than on deposit liabilities and other bank borrowings	(19,229)	(19,170)	(57,235)	(58,648)
Allowance for borrowed funds used during construction	737	740	1,918	1,877
Allowance for equity funds used during construction	2,057	1,937	5,366	4,933
Income before income taxes	80,660	75,543	189,380	212,595
Income taxes	29,516	27,264	70,406	76,302
Net income	51,144	48,279	118,974	136,293
Preferred stock dividends of subsidiaries	471	471	1,417	1,417
Net income for common stock	$ 50,673	$ 47,808	$ 117,557	$ 134,876
Basic earnings per common share (in dollars per share)	$ 0.47	$ 0.47	$ 1.11	$ 1.33
Diluted earnings per common share (in dollars per share)	0.47	0.46	1.11	1.32
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)	107,457	102,416	106,067	101,768
Net effect of potentially dilutive shares (in shares)	281	610	280	710
Adjusted weighted-average shares (in shares)	107,738	103,026	106,347	102,478
Electric utility
Revenues
Total revenues	$ 648,127	$ 803,565	$ 1,779,732	$ 2,262,056
Expenses
Total expenses	565,470	727,409	1,573,278	2,045,166
Operating income (loss)
Total operating income	82,657	76,156	206,454	216,890
Income before income taxes	68,894	62,419	164,568	174,711
Income taxes	25,390	23,042	60,351	64,686
Net income	43,504	39,377	104,217	110,025
Preferred stock dividends of subsidiaries	498	498	1,496	1,496
Net income for common stock	43,006	38,879	102,721	108,529
Bank
Revenues
Total revenues	69,091	63,536	199,222	187,771
Expenses
Total expenses	48,289	43,030	138,063	126,778
Operating income (loss)
Total operating income	20,802	20,506	61,159	60,993
Income before income taxes	20,802	20,506	61,159	60,994
Income taxes	7,351	7,253	21,382	21,806
Net income	13,451	13,253	39,777	39,188
Net income for common stock	13,451	13,253	39,777	39,188
Other
Revenues
Total revenues	(42)	(5)	(4)	(325)
Expenses
Total expenses	6,322	4,621	28,278	13,125
Operating income (loss)
Total operating income	(6,364)	(4,626)	(28,282)	(13,450)
Income before income taxes	(9,036)	(7,382)	(36,347)	(23,110)
Income taxes	(3,225)	(3,031)	(11,327)	(10,190)
Net income	(5,811)	(4,351)	(25,020)	(12,920)
Preferred stock dividends of subsidiaries	(27)	(27)	(79)	(79)
Net income for common stock	$ (5,784)	$ (4,324)	$ (24,941)	$ (12,841)