Selected Balance Sheet Data

12 Months Ended

Dec. 31, 2017

Balance Sheet Related Disclosures [Abstract]

Selected Balance Sheet Data

Selected Balance Sheet Data

(Thousands of Dollars)	Dec. 31, 2017			Dec. 31, 2016
Accounts receivable, net (a)
Accounts receivable	$	68,073		$	58,896
Less allowance for bad debts	(4,873		)	(4,865		)
	$	63,200		$	54,031

^(a)  Accounts receivable, net includes $3.4 million and an immaterial amount due from affiliates for 2017 and 2016, respectively.

(Thousands of Dollars)	Dec. 31, 2017		Dec. 31, 2016
Inventories
Materials and supplies	$	6,916	$	6,582
Fuel	3,866		4,743
Natural gas	6,976		6,984
	$	17,758	$	18,309

(Thousands of Dollars)	Dec. 31, 2017			Dec. 31, 2016
Property, plant and equipment, net
Electric plant	$	2,602,671		$	2,499,401
Natural gas plant	326,723			294,986
Common and other property	181,105			156,316
CWIP	148,770			118,822
Total property, plant and equipment	3,259,269			3,069,525
Less accumulated depreciation	(1,170,541		)	(1,121,888		)
	$	2,088,728		$	1,947,637