Quarterly Financial Data (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
	(Dollars in millions, except per share amounts)
2014
Operating revenues	$	4,538	4,541	4,514		4,438	18,031
Operating income	653		655	619		483	2,410
Net income	203		193	188		188	772
Basic earnings per common share	0.35		0.34	0.33		0.33	1.36
Diluted earnings per common share	0.35		0.34	0.33		0.33	1.36
2013
Operating revenues	$	4,513	4,525	4,515		4,542	18,095
Operating income (loss)	782		715	(685	)	641	1,453
Net income (loss)	298		269	(1,045	)	239	(239	)
Basic earnings (loss) per common share	0.48		0.45	(1.76	)	0.41	(0.40	)
Diluted earnings (loss) per common share	0.48		0.44	(1.76	)	0.41	(0.40	)