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 (a)
Accounts receivable	$	56,604		$	55,929
Less allowance for bad debts		(4,766	)		(4,262	)
	$	51,838		$	51,667
Inventories
Materials and supplies	$	5,838		$	5,564
Fuel		9,335			10,819
Natural gas		10,530			10,233
	$	25,703		$	26,616

(a) Accounts receivable, net includes $3 due from affiliates as of Dec. 31, 2010.

(Thousands of Dollars)	Dec. 31, 2011			Dec. 31, 2010
Property, plant and equipment, net
Electric plant	$	1,684,537		$	1,590,713
Natural gas plant		213,665			199,224
Common and other property		113,597			123,793
Construction work in progress		54,627			42,874
Total property, plant and equipment		2,066,426			1,956,604
Less accumulated depreciation		(858,728	)		(826,262	)
	$	1,207,698		$	1,130,342