CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Operating revenue:
Electric	$ 475,580	$ 461,657	$ 1,109,133	$ 1,076,291
Gas	183,935	180,728	571,378	565,493
Other	3,401	101	7,780	520
Total operating revenue	662,916	642,486	1,688,291	1,642,304
Energy costs:
Purchased electricity	114,627	112,543	295,785	287,587
Electric generation fuel	34,795	40,737	110,232	99,823
Residential exchange	(23,621)	(14,963)	(53,624)	(37,515)
Purchased gas	76,272	79,487	267,578	269,470
Unrealized (gain) loss on derivative instruments, net	(17,094)	27,376	(24,934)	(48,316)
Utility operations and maintenance	134,883	130,286	278,960	259,521
Non-utility expense and other	2,293	(959)	5,712	(1,953)
Depreciation	92,462	90,301	183,646	178,480
Amortization	12,735	6,433	23,270	12,177
Conservation amortization	22,526	22,469	51,508	56,576
Taxes other than income taxes	67,772	53,695	168,590	153,638
Total operating expenses	517,650	547,405	1,306,723	1,229,488
Operating income	145,266	95,081	381,568	412,816
Other income (deductions):
Other income	4,621	10,844	8,863	22,857
Other expense	(1,644)	(1,454)	(3,226)	(2,996)
Non-hedged interest rate derivative expense	(1,360)	1,232	(2,107)	2,260
Interest charges:
AFUDC	1,562	3,162	2,714	7,810
Interest expense	(92,173)	(108,917)	(182,428)	(204,733)
Income (loss) before income taxes	56,272	(52)	205,384	238,014
Income tax (benefit) expense	15,159	(957)	56,679	69,634
Net income (loss)	41,113	905	148,705	168,380
Subsidiaries [Member]
Operating revenue:
Electric	475,580	461,657	1,109,133	1,076,291
Gas	183,935	180,728	571,378	565,493
Other	3,401	101	7,780	409
Total operating revenue	662,916	642,486	1,688,291	1,642,193
Energy costs:
Purchased electricity	114,627	112,543	295,785	287,587
Electric generation fuel	34,795	40,737	110,232	99,823
Residential exchange	(23,621)	(14,963)	(53,624)	(37,515)
Purchased gas	76,272	79,487	267,578	269,470
Unrealized (gain) loss on derivative instruments, net	(17,094)	27,376	(24,364)	(45,365)
Utility operations and maintenance	134,883	130,286	278,960	259,521
Non-utility expense and other	5,374	3,028	11,548	6,120
Depreciation	92,462	90,301	183,646	178,480
Amortization	12,735	6,433	23,270	12,177
Conservation amortization	22,526	22,469	51,508	56,576
Taxes other than income taxes	67,772	53,695	168,590	153,638
Total operating expenses	520,731	551,392	1,313,129	1,240,512
Operating income	142,185	91,094	375,162	401,681
Other income (deductions):
Other income	4,621	10,846	8,860	22,857
Other expense	(1,644)	(1,454)	(3,226)	(2,996)
Interest charges:
AFUDC	1,562	3,162	2,714	7,810
Interest expense	(65,522)	(65,773)	(129,659)	(131,749)
Interest expense on parent note	(27)	(32)	(52)	(61)
Income (loss) before income taxes	81,175	37,843	253,799	297,542
Income tax (benefit) expense	23,341	11,180	74,883	90,941
Net income (loss)	$ 57,834	$ 26,663	$ 178,916	$ 206,601