Retirement Plans (Tables)

6 Months Ended

Jun. 30, 2016

Retirement Plans [Abstract]

Net Periodic Benefit Cost

	Pension Benefits
	For the three months ended				For the six months ended
	June 30,				June 30,
($ in millions)	2016		2015		2016		2015
Components of net periodic pension benefit cost
Service cost	$	34	$	14	$	47	$	27
Interest cost on projected benefit obligation		42		22		65		44
Expected return on plan assets		(65)		(32)		(92)		(64)
Amortization of unrecognized loss		11		6		21		13
Net periodic pension benefit cost	$	22	$	10	$	41	$	20

	Postretirement Benefits
	Other Than Pensions (OPEB)
	For the three months ended				For the six months ended
	June 30,				June 30,
($ in millions)	2016		2015		2016		2015
Components of net periodic postretirement benefit cost
Service cost	$	5	$	4	$	8	$	9
Interest cost on projected benefit obligation		10		8		17		15
Amortization of prior service cost/(credit)		(2)		(1)		(5)		(2)
Amortization of unrecognized loss		-		2		1		5
Net periodic postretirement benefit cost	$	13	$	13	$	21	$	27