Supplementary Quarterly Financial Information (Unaudited ) (Tables)

12 Months Ended

Dec. 31, 2014

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

	First Quarter		Second Quarter		Third Quarter		Fourth Quarter		Total Year to Date
	(In millions)
2014
Operating Revenues	$	1,410	$	1,281	$	1,357	$	1,234	$	5,282
Operating Income	$	271	$	259	$	272	$	250	$	1,052
Net Income	$	137	$	130	$	136	$	129	$	532
2013
Operating Revenues	$	1,219	$	1,265	$	1,457	$	1,256	$	5,197
Operating Income	$	235	$	202	$	338	$	225	$	1,000
Net Income	$	116	$	90	$	180	$	101	$	487