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
Accounts receivable	$	103,704		$	80,569
Less allowance for bad debts	(7,090		)	(6,379		)
	$	96,614		$	74,190

(Thousands of Dollars)	Sept. 30, 2017		Dec. 31, 2016
Inventories
Materials and supplies	$	26,877	$	25,453
Fuel	14,473		13,052
	$	41,350	$	38,505

(Thousands of Dollars)	Sept. 30, 2017			Dec. 31, 2016
Property, plant and equipment, net
Electric plant	$	6,653,228		$	6,362,189
Construction work in progress	312,445			260,327
Total property, plant and equipment	6,965,673			6,622,516
Less accumulated depreciation	(2,018,559		)	(1,926,697		)
	$	4,947,114		$	4,695,819