CONSOLIDATED STATEMENTS OF REVENUES AND EXPENSES (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating revenues:
Sales to Members	$ 1,204,008	$ 1,224,238	$ 1,292,667
Sales to non-Members	120,102	166,040	1,478
Total operating revenues	1,324,110	1,390,278	1,294,145
Operating expenses:
Fuel	516,223	531,147	501,113
Production	371,909	357,069	332,236
Depreciation and amortization	160,849	199,040	131,491
Purchased power	50,022	56,634	59,076
Accretion	19,554	18,249	17,131
Deferral of Hawk Road and Smith Energy Facilities effect on net margin	(16,280)	(9,681)	13,849
Total operating expenses	1,102,277	1,152,458	1,054,896
Operating margin	221,833	237,820	239,249
Other income:
Investment income	28,684	29,496	30,208
Gain on termination of Rocky Mountain transactions	18,976
Amortization of deferred gains	4,535	5,660	5,660
Allowance for equity funds used during construction	2,879	2,904	2,417
Other	6,413	6,204	5,366
Total other income	61,487	44,264	43,651
Interest charges:
Interest expense	307,482	296,138	266,641
Allowance for debt funds used during construction	(83,892)	(72,692)	(41,593)
Amortization of debt discount and expense	20,410	20,901	24,119
Net interest charges	244,000	244,347	249,167
Net margin	$ 39,320	$ 37,737	$ 33,733