Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Schedule of quarterly financial data (unaudited)

	Operating Revenues		Operating Income	Net Income (Loss)
	(Dollars in millions)
2016
First quarter (predecessor)	$	2,051	362	128
Second quarter (predecessor)	2,057		375	156
Third quarter (predecessor)	2,033		354	143
Fourth quarter (predecessor)	2,032		354	250
Total	$	8,173	1,445	677
2017
First quarter (predecessor)	$	2,048	337	95
Second quarter (predecessor)	2,062		353	154
Third quarter (predecessor)	2,059		349	157
Month ended October 31 (predecessor)	701		112	19
Two months ended December 31 (successor)	1,407		158	(141	)
Total	$	8,277	1,309	284