Selected Balance Sheet Data

3 Months Ended

Mar. 31, 2018

Balance Sheet Related Disclosures [Abstract]

Selected Balance Sheet Data

Selected Balance Sheet Data

(Thousands of Dollars)	March 31, 2018			Dec. 31, 2017
Accounts receivable, net
Accounts receivable	$	94,741		$	85,929
Less allowance for bad debts	(6,204		)	(6,348		)
	$	88,537		$	79,581

(Thousands of Dollars)	March 31, 2018		Dec. 31, 2017
Inventories
Materials and supplies	$	26,483	$	26,218
Fuel	7,932		14,215
	$	34,415	$	40,433

(Thousands of Dollars)	March 31, 2018			Dec. 31, 2017
Property, plant and equipment, net
Electric plant	$	6,908,735		$	6,765,371
Construction work in progress	306,920			351,875
Total property, plant and equipment	7,215,655			7,117,246
Less accumulated depreciation	(2,058,105		)	(2,021,637		)
	$	5,157,550		$	5,095,609