Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Schedule of Property, Plant and Equipment

Property, plant and equipment consisted of the following assets:

(millions)	Estimated Useful Lives	December 31, 2019			December 31, 2018
Electric generation	21-56 years	$	5,370		$	5,038
Electric transmission	28-77 years		940			880
Electric distribution	14-56 years		2,732			2,568
Gas transmission and distribution	16-77 years		1,848			1,678
General plant and other	8-43 years		675			613
Total cost			11,565			10,777
Less accumulated depreciation			(3,472	)		(3,214	)
Construction work in progress			1,038			673
Total property, plant and equipment, net		$	9,131		$	8,236