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	$	341,737		$	329,523
Less allowance for bad debts		(24,698	)		(24,054	)
	$	317,039		$	305,469
Inventories
Materials and supplies	$	53,318		$	51,615
Fuel		94,874			67,187
Natural gas		105,805			104,256
	$	253,997		$	223,058
Property, plant and equipment, net
Electric plant	$	9,469,434		$	9,003,103
Natural gas plant		2,456,275			2,284,212
Common and other property		763,513			757,059
Plant to be retired (a)		151,184			236,606
Construction work in progress		242,095			231,636
Total property, plant and equipment		13,082,501			12,512,616
Less accumulated depreciation		(3,606,930	)		(3,312,060	)
	$	9,475,571		$	9,200,556

(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.