Selected Balance Sheet Data

9 Months Ended

Sep. 30, 2017

Balance Sheet Related Disclosures [Abstract]

Selected Balance Sheet Data

Selected Balance Sheet Data

(Thousands of Dollars)	Sept. 30, 2017			Dec. 31, 2016
Accounts receivable, net (a)
Accounts receivable	$	55,619		$	58,896
Less allowance for bad debts	(4,405		)	(4,865		)
	$	51,214		$	54,031

^(a)  Accounts receivable, net includes an immaterial amount due from affiliates as of Sept. 30, 2017 and Dec. 31, 2016, respectively.

(Thousands of Dollars)	Sept. 30, 2017		Dec. 31, 2016
Inventories
Materials and supplies	$	7,417	$	6,582
Fuel	3,898		4,743
Natural gas	8,792		6,984
	$	20,107	$	18,309

(Thousands of Dollars)	Sept. 30, 2017			Dec. 31, 2016
Property, plant and equipment, net
Electric plant	$	2,553,562		$	2,499,401
Natural gas plant	317,902			294,986
Common and other property	185,612			156,316
Construction work in progress	151,299			118,822
Total property, plant and equipment	3,208,375			3,069,525
Less accumulated depreciation	(1,175,847		)	(1,121,888		)
	$	2,032,528		$	1,947,637