Selected Balance Sheet Data (Tables)

3 Months Ended

Mar. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Accounts Receivable, Net

(Millions of Dollars)	March 31, 2020			Dec. 31, 2019
Accounts receivable, net
Accounts receivable	$	92.4		$	98.0
Less allowance for bad debts	(5.9		)	(5.3		)
Accounts receivable, net	$	86.5		$	92.7

Inventories

(Millions of Dollars)	March 31, 2020		Dec. 31, 2019
Inventories
Materials and supplies	$	26.2	$	24.7
Fuel	5.7		6.3
Total inventories	$	31.9	$	31.0

Property, Plant and Equipment, Net

(Millions of Dollars)	March 31, 2020			Dec. 31, 2019
Property, plant and equipment, net
Electric plant	$	8,502.1		$	8,453.0
Construction work in progress	616.9			485.4
Total property, plant and equipment	9,119.0			8,938.4
Less accumulated depreciation	(2,344.2		)	(2,306.8		)
Property, plant and equipment, net	$	6,774.8		$	6,631.6