Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2018

Accounting Standards Update 2014-09 [Member]

Schedule Of Impact Of Adoption Of ASU 2017-07

	For the three months ended June 30, 2018
					Amounts without
			Adjustments		Adoption of
($ in millions)	As Reported		for ASC 606		ASC 606
Revenue	$	2,162	$	(2)	$	2,160
Operating expenses		1,795		6		1,801
Operating income	$	367	$	(8)	$	359
	For the six months ended June 30, 2018
					Amounts without
			Adjustments		Adoption of
($ in millions)	As Reported		for ASC 606		ASC 606
Revenue	$	4,361	$	(8)	$	4,353
Operating expenses		3,628		7		3,635
Operating income	$	733	$	(15)	$	718