Retirement Plans (Tables)

9 Months Ended

Sep. 30, 2015

Retirement Plans [Abstract]

Net Periodic Benefit Cost

	Pension Benefits
	For the three months ended				For the nine months ended
	September 30,				September 30,
	2015		2014		2015		2014
($ in millions)
Components of net periodic pension benefit cost
Service cost	$	14	$	9	$	41	$	29
Interest cost on projected benefit obligation		22		19		66		59
Expected return on plan assets		(32)		(23)		(96)		(70)
Amortization of unrecognized loss		9		5		22		14
Net periodic pension benefit cost	$	13	$	10	$	33	$	32

	Postretirement Benefits
	Other Than Pensions (OPEB)
	For the three months ended				For the nine months ended
	September 30,				September 30,
	2015		2014		2015		2014
($ in millions)
Components of net periodic postretirement benefit cost
Service cost	$	5	$	3	$	14	$	8
Interest cost on projected benefit obligation		7		5		22		15
Amortization of prior service cost/(credit)		(1)		(1)		(3)		(3)
Amortization of unrecognized loss		1		1		6		2
Net periodic postretirement benefit cost	$	12	$	8	$	39	$	22