Retirement Plans (Tables)

9 Months Ended

Sep. 30, 2017

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)	2017		2016		2017		2016
Components of total pension benefit cost
Service cost	$	26	$	16	$	76	$	63
Interest cost on projected benefit obligation		27		24		94		89
Expected return on plan assets		(43)		(30)		(139)		(122)
Amortization of unrecognized loss		6		9		23		30
Net periodic pension benefit cost	$	16	$	19	$	54	$	60
Pension settlement costs		15		-		77		-
Total pension benefit cost	$	31	$	19	$	131	$	60

	Postretirement Benefits
	For the three months ended				For the nine months ended
	September 30,				September 30,
($ in millions)	2017		2016		2017		2016
Components of net periodic postretirement benefit cost
Service cost	$	5	$	6	$	16	$	14
Interest cost on projected benefit obligation		11		10		30		27
Amortization of prior service cost/(credit)		(2)		(2)		(7)		(7)
Amortization of unrecognized (gain) loss		(1)		-		-		1
Net periodic postretirement benefit cost	$	13	$	14	$	39	$	35