QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

Accordingly, comparisons among quarters of a year may not represent overall trends and changes in operations.

	First Quarter			Second Quarter		Third Quarter		Fourth Quarter
(in millions)	2017
Operating Revenue	$	268		$	352	$	417	$	304
Operating Income	37			107		138		44
Net Income	21			61		82		13
	2016
Operating Revenue	$	243		$	317	$	394	$	281
Operating Income	12			72		122		37
Net Income (Loss)	(1		)	41		72		12