Summary of Significant Accounting Policies Inventory (Tables)

12 Months Ended

Dec. 31, 2020

Balance Sheet Related Disclosure - Inventory [Abstract]

Public Utilities, Inventory

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

(Millions of Dollars)	Dec. 31, 2020		Dec. 31, 2019
Inventories
Materials and supplies	$	63	$	63
Fuel	73		77
Natural gas	53		52
Total inventories	$	189	$	192