CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Electric plant:
In service	$ 7,506,707	$ 7,335,866
Less: Accumulated provision for depreciation	(3,472,087)	(3,328,585)
Total in service	4,034,620	4,007,281
Nuclear fuel, at amortized cost	321,196	284,205
Construction work in progress	2,240,920	1,784,264
Total electric plant	6,596,736	6,075,750
Investments and funds:
Nuclear decommissioning trust fund	300,785	268,597
Deposit on Rocky Mountain transactions	14,392	132,048
Investment in associated companies	60,770	57,626
Long-term investments	77,022	80,055
Restricted cash	8,953	43,070
Other, at cost	1,084	3,564
Total investments and funds	463,006	584,960
Current assets:
Cash and cash equivalents	298,565	443,671
Restricted short-term investments	64,671	106,676
Receivables	134,896	124,650
Inventories, at average cost	263,949	246,795
Prepayments and other current assets	16,073	16,175
Total current assets	778,154	937,967
Deferred charges and other assets
Deferred debt expense, being amortized	63,210	67,470
Regulatory assets	352,902	351,547
Other	60,558	61,135
Total deferred charges	476,670	480,152
Total assets	8,314,566	8,078,829
Capitalization:
Patronage capital and membership fees	673,009	633,689
Accumulated other comprehensive margin	903	618
Total patronage capital and membership fees and accumulated other comprehensive margin (deficit)	673,912	634,307
Long-term debt	5,784,130	5,562,925
Obligations under capital leases	135,943	146,781
Obligation under Rocky Mountain transactions	14,392	132,048
Total capitalization	6,608,377	6,476,061
Current liabilities:
Long-term debt and capital leases due within one year	168,393	172,818
Short-term borrowings	569,480	461,093
Accounts payable	145,451	134,095
Accrued interest	58,649	91,106
Accrued and withheld taxes	4,881	21,118
Members power bill prepayments, current	65,079	66,819
Other current liabilities	19,539	25,080
Total current liabilities	1,031,472	972,129
Deferred credits and other liabilities:
Gain on sale of plant, being amortized	23,638	26,113
Asset retirement obligations	381,362	298,758
Member power bill prepayments, non-current	40,853	35,500
Power sale agreement, being amortized	40,355	54,816
Regulatory liabilities	129,985	164,000
Other	58,524	51,452
Total deferred credits and other liabilities	674,717	630,639
Total equity and liabilities	8,314,566	8,078,829
Commitments and Contingencies (Notes 1, 9, 11 and 13)