Summarized Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2021

Quarterly Financial Information Disclosure [Abstract]

Summarized Quarterly Financial Data (Unaudited)

	Quarter Ended
(Millions of Dollars)	March 31, 2021		June 30, 2021		Sept. 30, 2021		Dec. 31, 2021
Operating revenues	$	1,057	$	911	$	1,081	$	1,134
Operating income	196		161		290		176
Net income	129		108		218		133

	Quarter Ended
(Millions of Dollars)	March 31, 2020		June 30, 2020		Sept. 30, 2020		Dec. 31, 2020
Operating revenues	$	1,057	$	911	$	1,081	$	1,134
Operating income	196		161		290		176
Net income	129		108		218		133