Selected Balance Sheet Data

12 Months Ended

Dec. 31, 2011

Selected Balance Sheet Data [Abstract]

Selected Balance Sheet Data

3.  Selected Balance Sheet Data

(Thousands of Dollars)	Dec. 31, 2011			Dec. 31, 2010
Accounts receivable, net
Accounts receivable	$	811,685		$	773,037
Less allowance for bad debts		(58,565	)		(54,563	)
	$	753,120		$	718,474
Inventories
Materials and supplies	$	202,699		$	196,081
Fuel		236,023			188,566
Natural gas		179,510			176,153
	$	618,232		$	560,800
Property, plant and equipment, net
Electric plant	$	27,254,541		$	24,993,582
Natural gas plant		3,676,754			3,463,343
Common and other property		1,546,643			1,555,287
Plant to be retired (a)		151,184			236,606
Construction work in progress		1,085,245			1,186,433
Total property, plant and equipment		33,714,367			31,435,251
Less accumulated depreciation		(11,658,351	)		(11,068,820	)
Nuclear fuel		1,939,299			1,837,697
Less accumulated amortization		(1,641,948	)		(1,541,046	)
	$	22,353,367		$	20,663,082

(a) In 2010, in response to the CACJA, the CPUC approved the early retirement of Cherokee Units 1, 2 and 3, Arapahoe Unit 3 and Valmont Unit 5 between 2011 and 2017.  Amounts are presented net of accumulated depreciation.  See Item 1 – Public Utility Regulation for further discussion.