Consolidated Statements of Revenues and Expenses - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating revenues:
Sales to Members	$ 385,758	$ 430,883	$ 1,106,975	$ 1,158,134
Sales to non-Members	148	130	220	383
Total operating revenues	385,906	431,013	1,107,195	1,158,517
Operating expenses:
Fuel	143,767	178,516	366,405	404,056
Production	93,657	105,681	293,930	312,332
Depreciation and amortization	56,143	54,719	167,983	162,606
Purchased power	14,345	13,109	44,222	39,254
Accretion	9,224	8,059	27,333	24,099
Total operating expenses	317,136	360,084	899,873	942,347
Operating margin	68,770	70,929	207,322	216,170
Other income:
Investment income	14,850	12,578	44,509	37,628
Other	627	1,531	1,908	6,259
Total other income	15,477	14,109	46,417	43,887
Interest charges:
Interest expense	93,809	93,544	280,621	273,066
Allowance for debt funds used during construction	(33,517)	(30,135)	(99,953)	(84,460)
Amortization of debt discount and expense	3,150	2,999	9,386	8,946
Net interest charges	63,442	66,408	190,054	197,552
Net margin	$ 20,805	$ 18,630	$ 63,685	$ 62,505