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Selected Balance Sheet Data
 3 Months Ended
Mar. 31, 2012
Selected Balance Sheet Data [Abstract]  
Selected Balance Sheet Data
3.
Selected Balance Sheet Data

 
(Thousands of Dollars)
 
March 31, 2012
 
 
Dec. 31, 2011
 
Accounts receivable, net
 
 
 
 
 
 
    Accounts receivable
 
$
776,140
 
 
$
811,685
 
    Less allowance for bad debts
 
 
(57,995
)
 
 
(58,565
)
 
$
718,145
 
 
$
753,120
 
Inventories
 
 
 
 
 
 
 
 
    Materials and supplies
 
$
207,729
 
 
$
202,699
 
    Fuel
 
 
176,874
 
 
 
236,023
 
    Natural gas
 
 
89,756
 
 
 
179,510
 
 
 
$
474,359
 
 
$
618,232
 
Property, plant and equipment, net
 
 
 
 
 
 
 
 
    Electric plant
 
$
27,393,092
 
 
$
27,254,541
 
    Natural gas plant
 
 
3,700,424
 
 
 
3,676,754
 
    Common and other property
 
 
1,484,878
 
 
 
1,546,643
 
    Plant to be retired (a)
 
 
115,401
 
 
 
151,184
 
    Construction work in progress
 
 
1,315,390
 
 
 
1,085,245
 
          Total property, plant and equipment
 
 
34,009,185
 
 
 
33,714,367
 
    Less accumulated depreciation
 
 
(11,731,341
)
 
 
(11,658,351
)
    Nuclear fuel
 
 
2,062,790
 
 
 
1,939,299
 
    Less accumulated amortization
 
 
(1,667,948
)
 
 
(1,641,948
)
 
$
22,672,686
 
 
$
22,353,367
 
 
(a)
In 2010, in response to the Clean Air Clean Jobs Act (CACJA), the Colorado Public Utilities Commission (CPUC) approved the early retirement of Cherokee Units 1, 2 and 3, Arapahoe Unit 3 and Valmont Unit 5 between 2011 and 2017.  In 2011, Cherokee Unit 2 was taken out of service.  Amounts are presented net of accumulated depreciation.