Summary of Significant Accounting Policies Inventory (Tables)

12 Months Ended

Dec. 31, 2019

Balance Sheet Related Disclosure - Inventory [Abstract]

Public Utilities, Inventory

Inventory is recorded at average cost and consisted of the following:

(Millions of Dollars)	Dec. 31, 2019		Dec. 31, 2018
Inventories
Materials and supplies	$	270	$	271
Fuel	191		170
Natural gas	83		107
Total inventories	$	544	$	548