Condensed Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net margin	$ 22,024	$ 13,520
Adjustments to reconcile net margin to net cash provided by operating activities:
Depreciation and amortization, including nuclear fuel	68,384	77,580
Accretion cost	5,630	4,857
Amortization of deferred gains	(447)	(1,415)
Allowance for equity funds used during construction	(752)	(851)
Deferred outage costs	(23,911)	(12,604)
Deferral of Hawk Road and Smith Energy Facilities effect on net margin	(11,890)	(12,075)
Gain on sale of investments	(3,529)	(2,362)
Regulatory deferral of costs associated with nuclear decommissioning	(97)	(622)
Other	(2,119)	(1,923)
Change in operating assets and liabilities:
Receivables	6,124	(12,349)
Inventories	10,181	511
Prepayments and other current assets	1,794	1,525
Accounts payable	(70,675)	(25,594)
Accrued interest	14,451	(21,844)
Accrued taxes	4,634	(12,704)
Other current liabilities	(2,892)	1,227
Member power bill prepayments	84,903	5,570
Total adjustments	79,789	(13,073)
Net cash provided by operating activities	101,813	447
Cash flows from investing activities:
Property additions	(180,365)	(210,050)
Activity in decommissioning fund-Purchases	(106,460)	(288,010)
Activity in decommissioning fund-Proceeds	105,148	287,040
Increase in restricted cash	(4,410)	(8,671)
Increase in restricted short-term investments	(139,127)	(3,850)
Activity in other long-term investments-Purchases	(6,394)	(486)
Activity in other long-term investments-Proceeds	6,633	8,600
Activity on interest rate options-Collateral returned	(17,440)
Activity on interest rate options-Collateral received	21,850	8,670
Other	2,076	12,825
Net cash used in investing activities	(318,489)	(193,932)
Cash flows from financing activities:
Long-term debt proceeds	20,734	69,139
Long-term debt payments	(215,663)	(42,907)
Increase in short-term borrowings, net	351,944	123,921
Other	610	2,029
Net cash provided by financing activities	157,625	152,182
Net decrease in cash and cash equivalents	(59,051)	(41,303)
Cash and cash equivalents at beginning of period	298,565	443,671
Cash and cash equivalents at end of period	239,514	402,368
Cash paid for-
Interest (net of amounts capitalized)	35,312	74,287
Supplemental disclosure of non-cash investing and financing activities:
Change in plant expenditures included in accounts payable	$ 1,420	$ (27,699)