CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Electric plant:
In service	$ 8,050,103	$ 7,506,707
Less: Accumulated provision for depreciation	(3,615,375)	(3,472,087)
Total in service	4,434,728	4,034,620
Nuclear fuel, at amortized cost	341,012	321,196
Construction work in progress	2,212,224	2,240,920
Total electric plant	6,987,964	6,596,736
Investments and funds:
Nuclear decommissioning trust fund	343,698	300,785
Deposit on Rocky Mountain transactions	15,379	14,392
Investment in associated companies	66,437	60,770
Long-term investments	81,720	77,022
Restricted cash	34,975	8,953
Other	719	1,084
Total investments and funds	542,928	463,006
Current assets:
Cash and cash equivalents	408,193	298,565
Restricted short-term investments	272,686	64,671
Receivables	128,992	134,896
Inventories, at average cost	286,168	263,949
Prepayments and other current assets	16,894	16,073
Total current assets	1,112,933	778,154
Deferred charges and other assets:
Deferred debt expense, being amortized	57,175	63,210
Regulatory assets	331,108	352,902
Other	63,104	60,558
Total deferred charges	451,387	476,670
Total assets	9,095,212	8,314,566
Capitalization:
Patronage capital and membership fees	714,489	673,009
Accumulated other comprehensive margin	(549)	903
Total patronage capital and membership fees and accumulated other comprehensive margin	713,940	673,912
Long-term debt	6,817,518	5,784,130
Obligations under capital leases	121,731	135,943
Obligation under Rocky Mountain transactions	15,379	14,392
Total capitalization	7,668,568	6,608,377
Current liabilities:
Long-term debt and capital leases due within one year	152,153	168,393
Short-term borrowings	279,407	569,480
Accounts payable	101,529	145,451
Accrued interest	58,193	58,649
Accrued and withheld taxes	22,877	4,881
Members power bill prepayments, current	82,405	65,079
Other current liabilities	19,376	19,539
Total current liabilities	715,940	1,031,472
Deferred credits and other liabilities:
Gain on sale of plant, being amortized	22,157	23,638
Asset retirement obligations	408,050	381,362
Member power bill prepayments, non-current	32,313	40,853
Power sale agreement, being amortized	26,107	40,355
Regulatory liabilities	158,789	129,985
Other	63,288	58,524
Total deferred credits and other liabilities	710,704	674,717
Total equity and liabilities	9,095,212	8,314,566
Commitments and Contingencies (Notes 1, 9, 11 and 12)