Consolidated Statements of Revenues and Expenses (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating revenues:
Total operating revenues	$ 366,239	$ 382,623	$ 1,038,857	$ 1,098,083
Operating expenses:
Fuel	131,925	138,704	282,677	349,146
Production	94,071	93,092	303,705	301,996
Depreciation and amortization	61,758	60,574	186,370	183,212
Purchased power	16,419	17,716	49,366	50,415
Accretion	14,204	13,328	40,830	36,361
Total operating expenses	318,377	323,414	862,948	921,130
Operating margin	47,862	59,209	175,909	176,953
Other income:
Investment income	11,672	14,144	36,210	45,129
Other	1,832	623	5,733	1,565
Total other income	13,504	14,767	41,943	46,694
Interest charges:
Interest expense	101,600	100,687	305,128	301,864
Allowance for debt funds used during construction	(51,518)	(47,909)	(153,595)	(138,246)
Amortization of debt discount and expense	2,813	2,912	8,482	8,764
Net interest charges	52,895	55,690	160,015	172,382
Net margin	8,471	18,286	57,837	51,265
Members
Operating revenues:
Total operating revenues	365,937	382,548	1,038,218	1,097,754
Non-Members
Operating revenues:
Total operating revenues	$ 302	$ 75	$ 639	$ 329