Consolidated Statements of Revenues and Expenses (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating revenues:
Total operating revenues	$ 358,127	$ 330,944	$ 734,458	$ 672,618
Operating expenses:
Fuel	113,531	79,596	221,596	150,752
Production	93,477	93,503	198,850	209,634
Depreciation and amortization	67,277	62,588	134,896	124,612
Purchased power	16,866	16,334	33,786	32,947
Accretion	13,941	13,391	27,722	26,626
Total operating expenses	305,092	265,412	616,850	544,571
Operating margin	53,035	65,532	117,608	128,047
Other income:
Investment income	12,130	11,604	24,090	24,538
Other	277	1,892	2,448	3,901
Total other income	12,407	13,496	26,538	28,439
Interest charges:
Interest expense	104,247	101,243	207,726	203,528
Allowance for debt funds used during construction	(54,810)	(51,047)	(108,449)	(102,077)
Amortization of debt discount and expense	2,860	2,670	5,766	5,669
Net interest charges	52,297	52,866	105,043	107,120
Net margin	13,145	26,162	39,103	49,366
Members
Operating revenues:
Total operating revenues	357,921	330,768	734,193	672,281
Non-Members
Operating revenues:
Total operating revenues	$ 206	$ 176	$ 265	$ 337