CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating revenue:
Electric	$ 669,090	$ 798,928
Natural Gas	371,031	304,668
Other	6,009	11,243
Total operating revenue	1,046,130	1,114,839
Energy costs:
Purchased electricity	165,742	270,702
Electric generation fuel	63,624	77,199
Residential exchange	(24,634)	(25,163)
Purchased natural gas	154,876	99,387
Unrealized (gain) loss on derivative instruments, net	48,541	(15,187)
Utility operations and maintenance	154,922	157,955
Non-utility expense and other	12,962	13,757
Depreciation & Amortization	164,816	180,697
Conservation amortization	27,393	33,286
Taxes other than income taxes	105,504	108,746
Total operating expenses	873,746	901,379
Operating income(loss)	172,384	213,460
Other income (expense):
Other income	14,059	13,564
Other expense	(2,282)	(1,776)
Interest charges:
AFUDC	3,643	3,350
Interest expense	(88,884)	(88,016)
Income (loss) before income taxes	98,920	140,582
Income tax (benefit) expense	3,984	8,428
Net income (loss)	94,936	132,154
Subsidiaries [Member]
Operating revenue:
Electric	669,090	798,928
Natural Gas	371,031	304,668
Other	6,009	11,243
Total operating revenue	1,046,130	1,114,839
Energy costs:
Purchased electricity	165,742	270,702
Electric generation fuel	63,624	77,199
Residential exchange	(24,634)	(25,163)
Purchased natural gas	154,876	99,387
Unrealized (gain) loss on derivative instruments, net	48,541	(15,187)
Utility operations and maintenance	154,922	157,955
Non-utility expense and other	12,735	13,077
Depreciation & Amortization	164,771	180,678
Conservation amortization	27,393	33,286
Taxes other than income taxes	105,504	108,746
Total operating expenses	873,474	900,680
Operating income(loss)	172,656	214,159
Other income (expense):
Other income	11,283	10,549
Other expense	(2,282)	(1,776)
Interest charges:
AFUDC	3,643	3,350
Interest expense	(60,714)	(60,150)
Income (loss) before income taxes	124,586	166,132
Income tax (benefit) expense	13,265	18,830
Net income (loss)	$ 111,321	$ 147,302