Selected Balance Sheet Data

9 Months Ended

Sep. 30, 2013

Balance Sheet Related Disclosures [Abstract]

Selected Balance Sheet Data

Selected Balance Sheet Data

(Thousands of Dollars)	Sept. 30, 2013			Dec. 31, 2012
Accounts receivable, net
Accounts receivable	$	86,377		$	66,789
Less allowance for bad debts	(5,118		)	(4,722		)
	$	81,259		$	62,067

(Thousands of Dollars)	Sept. 30, 2013		Dec. 31, 2012
Inventories
Materials and supplies	$	21,005	$	18,129
Fuel	15,890		13,208
	$	36,895	$	31,337

(Thousands of Dollars)	Sept. 30, 2013			Dec. 31, 2012
Property, plant and equipment, net
Electric plant	$	4,660,418		$	4,379,208
Construction work in progress	319,991			237,136
Total property, plant and equipment	4,980,409			4,616,344
Less accumulated depreciation	(1,806,222		)	(1,754,588		)
	$	3,174,187		$	2,861,756