Consolidated Statements of Revenues and Expenses (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating revenues:
Total operating revenues	$ 330,944	$ 358,860	$ 672,618	$ 715,460
Operating expenses:
Fuel	79,596	111,450	150,752	210,442
Production	93,503	105,584	209,634	208,904
Depreciation and amortization	62,588	60,334	124,612	122,638
Purchased power	16,334	16,635	32,947	32,699
Accretion	13,391	13,145	26,626	23,033
Total operating expenses	265,412	307,148	544,571	597,716
Operating margin	65,532	51,712	128,047	117,744
Other income:
Investment income	11,604	14,250	24,538	30,985
Other	1,892	(886)	3,901	942
Total other income	13,496	13,364	28,439	31,927
Interest charges:
Interest expense	101,243	99,729	203,528	201,177
Allowance for debt funds used during construction	(51,047)	(46,910)	(102,077)	(90,337)
Amortization of debt discount and expense	2,670	2,874	5,669	5,852
Net interest charges	52,866	55,693	107,120	116,692
Net margin	26,162	9,383	49,366	32,979
Members
Operating revenues:
Total operating revenues	330,768	358,736	672,281	715,206
Non-Members
Operating revenues:
Total operating revenues	$ 176	$ 124	$ 337	$ 254