CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Electric plant:
In service	$ 7,335,866	$ 6,672,253
Less: Accumulated provision for depreciation	(3,328,585)	(3,101,731)
Total in service	4,007,281	3,570,522
Nuclear fuel, at amortized cost	284,205	249,563
Construction work in progress	1,784,264	1,195,475
Total electric plant	6,075,750	5,015,560
Investments and funds:
Nuclear decommissioning trust fund	268,597	265,483
Deposit on Rocky Mountain transactions	132,048	123,573
Investment in associated companies	57,626	56,125
Long-term investments	80,055	79,212
Restricted cash	43,070
Other, at cost	3,564	3,570
Total investments and funds	584,960	527,963
Current assets:
Cash and cash equivalents	443,671	672,212
Restricted cash	613	6,300
Restricted short-term investments	106,676	97,286
Receivables	124,650	106,674
Inventories, at average cost	246,795	171,815
Prepayments and other current assets	15,562	13,416
Total current assets	937,967	1,067,703
Deferred charges and other assets
Deferred debt expense, being amortized	67,470	59,202
Regulatory assets	351,547	311,136
Other	61,135	15,498
Total deferred charges	480,152	385,836
Total assets	8,078,829	6,997,062
Capitalization:
Patronage capital and membership fees	633,689	595,952
Accumulated other comprehensive margin (deficit)	618	(469)
Total patronage capital and membership fees and accumulated other comprehensive margin (deficit)	634,307	595,483
Long-term debt	5,562,925	4,657,127
Obligations under capital leases	146,781	179,288
Obligation under Rocky Mountain transactions	132,048	123,573
Total capitalization	6,476,061	5,555,471
Current liabilities:
Long-term debt and capital leases due within one year	172,818	170,947
Short-term borrowings	461,093	305,959
Accounts payable	134,095	139,614
Accrued interest	91,106	76,435
Accrued and withheld taxes	21,118	27,171
Members power bill prepayments, current	66,819	71,496
Other current liabilities	25,080	18,567
Total current liabilities	972,129	810,189
Deferred credits and other liabilities:
Gain on sale of plant, being amortized	26,113	28,587
Asset retirement obligations	298,758	280,496
Member power bill prepayments, non-current	35,500	41,000
Power sale agreement, being amortized	54,816	69,480
Regulatory liabilities	164,000	170,235
Other	51,452	41,604
Total deferred credits and other liabilities	630,639	631,402
Total equity and liabilities	8,078,829	6,997,062
Commitments and Contingencies (Notes 1, 5, 9, 11 and 12)