Condensed Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Electric plant:
In service	$ 7,860,834	$ 7,506,707
Less: Accumulated provision for depreciation	(3,581,212)	(3,472,087)
Total in service	4,279,622	4,034,620
Nuclear fuel, at amortized cost	311,355	321,196
Construction work in progress	2,261,374	2,240,920
Total electric plant	6,852,351	6,596,736
Investments and funds:
Nuclear decommissioning trust fund	325,924	300,785
Deposit on Rocky Mountain transactions	15,128	14,392
Investment in associated companies	62,720	60,770
Long-term investments	78,353	77,022
Restricted cash	31,064	8,953
Other	472	1,084
Total investments and funds	513,661	463,006
Current assets:
Cash and cash equivalents	436,639	298,565
Restricted short-term investments	254,854	64,671
Receivables	136,973	134,896
Inventories, at average cost	277,633	263,949
Prepayments and other current assets	16,310	16,073
Total current assets	1,122,409	778,154
Deferred charges:
Deferred debt expense, being amortized	63,808	63,210
Regulatory assets	339,274	352,902
Other	43,818	60,558
Total deferred charges	446,900	476,670
Total assets	8,935,321	8,314,566
Capitalization:
Patronage capital and membership fees	739,639	673,009
Accumulated other comprehensive (deficit) margin	(194)	903
Total patronage capital and membership fees and accumulated other comprehensive margin	739,445	673,912
Long-term debt	6,076,645	5,784,130
Obligation under capital leases	126,187	135,943
Obligation under Rocky Mountain transactions	15,128	14,392
Total capitalization	6,957,405	6,608,377
Current liabilities:
Long-term debt and capital leases due within one year	447,388	168,393
Short-term borrowings	603,812	569,480
Accounts payable	82,790	145,451
Accrued interest	49,357	58,649
Accrued and withheld taxes	24,482	4,881
Member power bill prepayments, current	75,410	65,079
Other current liabilities	14,960	19,539
Total current liabilities	1,298,199	1,031,472
Deferred credits and other liabilities:
Gain on sale of plant, being amortized	22,528	23,638
Asset retirement obligations	394,724	381,362
Member power bill prepayments, non-current	32,613	40,853
Power sale agreement, being amortized	29,669	40,355
Regulatory liabilities	139,187	129,985
Other	60,996	58,524
Total deferred credits and other liabilities	679,717	674,717
Total equity and liabilities	$ 8,935,321	$ 8,314,566