Selected Balance Sheet Data

12 Months Ended

Dec. 31, 2012

Selected Balance Sheet Data [Abstract]

Selected Balance Sheet Data

3.  Selected Balance Sheet Data

(Thousands of Dollars)	Dec. 31, 2012			Dec. 31, 2011
Accounts receivable, net
Accounts receivable	$	66,789		$	70,410
Less allowance for bad debts		(4,722	)		(5,380	)
	$	62,067		$	65,030

(Thousands of Dollars)	Dec. 31, 2012		Dec. 31, 2011
Inventories
Materials and supplies	$	18,129	$	17,472
Fuel		13,208		18,103
	$	31,337	$	35,575

(Thousands of Dollars)	Dec. 31, 2012			Dec. 31, 2011
Property, plant and equipment, net
Electric plant	$	4,379,208		$	4,142,389
Construction work in progress		237,136			153,672
Total property, plant and equipment		4,616,344			4,296,061
Less accumulated depreciation		(1,754,588	)		(1,701,329	)
	$	2,861,756		$	2,594,732