Selected Balance Sheet Data

3 Months Ended

Mar. 31, 2013

Selected Balance Sheet Data [Abstract]

Selected Balance Sheet Data

3. Selected Balance Sheet Data

(Thousands of Dollars)	March 31, 2013			Dec. 31, 2012
Accounts receivable, net
Accounts receivable	$	63,520		$	66,789
Less allowance for bad debts		(4,570	)		(4,722	)
	$	58,950		$	62,067

(Thousands of Dollars)	March 31, 2013		Dec. 31, 2012
Inventories
Materials and supplies	$	18,932	$	18,129
Fuel		5,549		13,208
	$	24,481	$	31,337

(Thousands of Dollars)	March 31, 2013			Dec. 31, 2012
Property, plant and equipment, net
Electric plant	$	4,428,802		$	4,379,208
Construction work in progress		276,176			237,136
Total property, plant and equipment		4,704,978			4,616,344
Less accumulated depreciation		(1,773,702	)		(1,754,588	)
	$	2,931,276		$	2,861,756