Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2021

Balance Sheet Related Disclosures [Abstract]

Schedule of Utility Inventory [Table Text Block]

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

(Millions of Dollars)	Dec. 31, 2021		Dec. 31, 2020
Inventories
Materials and supplies	$	181	$	178
Fuel	81		90
Natural gas	47		27
Total inventories	$	309	$	295