Retirement Plans (Tables)

9 Months Ended

Sep. 30, 2016

Retirement Plans [Abstract]

Net Periodic Benefit Cost

	Pension Benefits
	For the three months ended				For the nine months ended
	September 30,				September 30,
($ in millions)	2016		2015		2016		2015
Components of net periodic pension benefit cost
Service cost	$	16	$	14	$	63	$	41
Interest cost on projected benefit obligation		24		22		89		66
Expected return on plan assets		(30)		(32)		(122)		(96)
Amortization of unrecognized loss		9		9		30		22
Net periodic pension benefit cost	$	19	$	13	$	60	$	33

	Postretirement Benefits
	Other Than Pensions (OPEB)
	For the three months ended				For the nine months ended
	September 30,				September 30,
($ in millions)	2016		2015		2016		2015
Components of net periodic postretirement benefit cost
Service cost	$	6	$	5	$	14	$	14
Interest cost on projected benefit obligation		10		7		27		22
Amortization of prior service cost/(credit)		(2)		(1)		(7)		(3)
Amortization of unrecognized loss		-		1		1		6
Net periodic postretirement benefit cost	$	14	$	12	$	35	$	39