Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2013

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)
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	)
2012
Operating revenues	$	4,610	4,612	4,571		4,583	18,376
Operating income	654		657	736		666	2,713
Net income	200		74	270		233	777
Basic earnings per common share	0.32		0.12	0.43		0.37	1.25
Diluted earnings per common share	0.32		0.12	0.43		0.37	1.25