Summarized Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2020

Quarterly Financial Information Disclosure [Abstract]

Summarized Quarterly Financial Data (Unaudited)

	Quarter Ended
(Amounts in millions, except per share data)	March 31, 2020		June 30, 2020		Sept. 30, 2020		Dec. 31, 2020
Operating revenues	$	2,811	$	2,586	$	3,182	$	2,947
Operating income	455		422		813		426
Net income	295		287		603		288
EPS total — basic	$	0.56	$	0.54	$	1.15	$	0.54
EPS total — diluted	0.56		0.54		1.14		0.54
Cash dividends declared per common share	0.43		0.43		0.43		0.43

	Quarter Ended
(Amounts in millions, except per share data)	March 31, 2019		June 30, 2019		Sept. 30, 2019		Dec. 31, 2019
Operating revenues	$	3,141	$	2,577	$	3,013	$	2,798
Operating income	486		410		758		450
Net income	315		238		527		292
EPS total — basic	$	0.61	$	0.46	$	1.02	$	0.56
EPS total — diluted	0.61		0.46		1.01		0.56
Cash dividends declared per common share	0.405		0.405		0.405		0.405