CONSOLIDATED STATEMENTS OF REVENUES AND EXPENSES - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating revenues:
Sales to Members	$ 1,506,807	$ 1,219,052	$ 1,314,869
Sales to non-Members	424	130,773	93,294
Total operating revenues	1,507,231	1,349,825	1,408,163
Operating expenses:
Fuel	513,258	441,738	515,729
Production	434,306	457,264	428,801
Depreciation and amortization	217,534	168,920	166,247
Purchased power	54,108	56,925	71,799
Accretion	32,361	26,108	24,616
Deferral of Hawk Road and Smith Energy Facilities effect on net margin	0	(58,588)	(58,426)
Total operating expenses	1,251,567	1,092,367	1,148,766
Operating margin	255,664	257,458	259,397
Other income:
Investment income	51,656	40,424	36,791
Amortization of deferred gains	1,788	1,788	1,788
Allowance for equity funds used during construction	788	675	1,172
Other	2,671	9,143	6,620
Total other income	56,903	52,030	46,371
Interest charges:
Interest expense	366,892	354,269	344,561
Allowance for debt funds used during construction	(116,634)	(108,667)	(102,081)
Amortization of debt discount and expense	11,964	15,545	16,653
Net interest charges	262,222	261,147	259,133
Net margin	$ 50,345	$ 48,341	$ 46,635