Retirement Plans (Tables)

9 Months Ended

Sep. 30, 2018

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)	2018		2017		2018		2017
Components of total pension benefit cost
Service cost	$	22	$	26	$	70	$	76
Interest cost on projected benefit obligation		31		27		91		94
Expected return on plan assets		(45)		(43)		(143)		(139)
Amortization of unrecognized loss		4		6		17		23
Net periodic pension benefit cost	$	12	$	16	$	35	$	54
Pension settlement costs		9		15		34		77
Total pension benefit cost	$	21	$	31	$	69	$	131
	Postretirement Benefits
	For the three months ended				For the nine months ended
	September 30,				September 30,
($ in millions)	2018		2017		2018		2017
Components of net periodic postretirement benefit cost
Service cost	$	5	$	5	$	16	$	16
Interest cost on projected benefit obligation		9		11		28		30
Amortization of prior service cost/(credit)		(1)		(2)		(6)		(7)
Amortization of unrecognized (gain) loss		-		(1)		1		-
Net periodic postretirement benefit cost	$	13	$	13	$	39	$	39