Selected Balance Sheet Data

6 Months Ended

Jun. 30, 2016

Balance Sheet Related Disclosures [Abstract]

Selected Balance Sheet Data

Selected Balance Sheet Data

(Thousands of Dollars)	June 30, 2016			Dec. 31, 2015
Accounts receivable, net
Accounts receivable	$	89,872		$	77,054
Less allowance for bad debts	(5,864		)	(5,888		)
	$	84,008		$	71,166

(Thousands of Dollars)	June 30, 2016		Dec. 31, 2015
Inventories
Materials and supplies	$	25,525	$	24,888
Fuel	6,132		12,658
	$	31,657	$	37,546

(Thousands of Dollars)	June 30, 2016			Dec. 31, 2015
Property, plant and equipment, net
Electric plant	$	6,119,713		$	5,933,764
Construction work in progress	277,974			236,697
Total property, plant and equipment	6,397,687			6,170,461
Less accumulated depreciation	(1,877,015		)	(1,821,638		)
	$	4,520,672		$	4,348,823