Consolidated Statements of Revenues and Expenses - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating revenues:
Sales to Members	$ 373,401	$ 354,144
Sales to non-Members	245	26
Total operating revenues	373,646	354,170
Operating expenses:
Fuel	120,447	103,915
Production	101,272	101,088
Depreciation and amortization	56,788	55,863
Purchased power	15,888	14,976
Accretion	9,320	8,998
Total operating expenses	303,715	284,840
Operating margin	69,931	69,330
Other income:
Investment income	13,964	14,819
Other	1,974	640
Total other income	15,938	15,459
Interest charges:
Interest expense	89,670	93,285
Allowance for debt funds used during construction	(34,199)	(33,087)
Amortization of debt discount and expense	2,998	3,137
Net interest charges	58,469	63,335
Net margin	$ 27,400	$ 21,454