Property Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Abstract]

Public Utility Property, Plant, and Equipment

Major classes of property, plant and equipment

(Millions of Dollars)	Dec. 31, 2019			Dec. 31, 2018
Property, plant and equipment
Electric plant	$	18,519.5		$	17,749.3
Natural gas plant	1,562.9			1,475.5
Common and other property	886.7			803.1
CWIP	846.3			615.1
Total property, plant and equipment	21,815.4			20,643.0
Less accumulated depreciation	(7,945.3		)	(7,454.8		)
Nuclear fuel	2,909.8			2,770.4
Less accumulated amortization	(2,535.9		)	(2,416.9		)
Property, plant and equipment, net	$	14,244.0		$	13,541.7

Schedule of Jointly Owned Utility Plants

Joint Ownership of Generation and Transmission Facilities

Jointly owned assets as of Dec. 31, 2019:

(Millions of Dollars)	Plant in Service		Accumulated Depreciation		CWIP		Percent Owned
Electric generation:
Sherco Unit 3	$	603.0	$	426.3	$	3.8	59	%
Sherco common facilities	144.7		102.7		1.9		80
Sherco substation	4.8		3.5		—		59
Electric transmission:
CapX2020	972.5		91.6		2.2		51
Grand Meadow	10.7		2.6		—		50
Total	$	1,735.7	$	626.7	$	7.9