CONSOLIDATED STATEMENTS OF REVENUES AND EXPENSES (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating revenues:
Sales to Members	$ 1,166,618	$ 1,204,008	$ 1,224,238
Sales to non-Members	78,758	120,102	166,040
Total operating revenues	1,245,376	1,324,110	1,390,278
Operating expenses:
Fuel	442,425	516,223	531,147
Production	369,730	371,909	357,069
Depreciation and amortization	158,375	160,849	199,040
Purchased power	56,084	50,022	56,634
Accretion	22,900	19,554	18,249
Deferral of Hawk Road and Smith Energy Facilities effect on net margin	(35,662)	(16,280)	(9,681)
Total operating expenses	1,013,852	1,102,277	1,152,458
Operating margin	231,524	221,833	237,820
Other income:
Investment income	33,558	28,684	29,496
Gain on termination of Rocky Mountain transactions		18,976
Amortization of deferred gains	1,788	4,535	5,660
Allowance for equity funds used during construction	2,397	2,879	2,904
Other	5,690	6,413	6,204
Total other income	43,433	61,487	44,264
Interest charges:
Interest expense	313,491	307,482	296,138
Allowance for debt funds used during construction	(95,886)	(83,892)	(72,692)
Amortization of debt discount and expense	15,872	20,410	20,901
Net interest charges	233,477	244,000	244,347
Net margin	$ 41,480	$ 39,320	$ 37,737