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	$	70,410		$	49,966
Less allowance for bad debts		(5,380	)		(5,095	)
	$	65,030		$	44,871
Inventories
Materials and supplies	$	17,472		$	15,093
Fuel		18,103			14,756
	$	35,575		$	29,849
Property, plant and equipment, net
Electric plant	$	4,142,389		$	3,826,202
Construction work in progress		153,672			221,025
Total property, plant and equipment		4,296,061			4,047,227
Less accumulated depreciation		(1,701,329	)		(1,645,961	)
	$	2,594,732		$	2,401,266