Selected Balance Sheet Data (Tables)

9 Months Ended

Sep. 30, 2012

Selected Balance Sheet Data [Abstract]

Accounts Receivable, Net

(Thousands of Dollars)	Sept. 30, 2012			Dec. 31, 2011
Accounts receivable, net (a)
Accounts receivable	$	53,444			$	56,604
Less allowance for bad debts		(3,990	)			(4,766	)
	$	49,454			$	51,838

(a) Accounts receivable, net includes $256 due from affiliates as of Sept. 30, 2012.

Inventories

(Thousands of Dollars)	Sept. 30, 2012		Dec. 31, 2011
Inventories
Materials and supplies	$	6,369	$	5,838
Fuel		6,960		9,335
Natural gas		8,450		10,530
	$	21,779	$	25,703

Property, Plant and Equipment, Net

(Thousands of Dollars)	Sept. 30, 2012			Dec. 31, 2011
Property, plant and equipment, net
Electric plant	$	1,744,066		$	1,684,537
Natural gas plant		219,630			213,665
Common and other property		110,494			113,597
Construction work in progress		74,910			54,627
Total property, plant and equipment		2,149,100			2,066,426
Less accumulated depreciation		(885,016	)		(858,728	)
	$	1,264,084		$	1,207,698