Retirement Plans (Tables)

6 Months Ended

Jun. 30, 2017

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)	2017		2016		2017		2016
Components of total pension benefit cost
Service cost	$	25	$	34	$	50	$	47
Interest cost on projected benefit obligation		33		42		67		65
Expected return on plan assets		(48)		(65)		(96)		(92)
Amortization of unrecognized loss		9		11		17		21
Net periodic pension benefit cost	$	19	$	22	$	38	$	41
Pension settlement costs		19		-		62		-
Total pension benefit cost	$	38	$	22	$	100	$	41

	Postretirement Benefits
	For the three months ended				For the six months ended
	June 30,				June 30,
($ in millions)	2017		2016		2017		2016
Components of net periodic postretirement benefit cost
Service cost	$	6	$	5	$	11	$	8
Interest cost on projected benefit obligation		9		10		19		17
Amortization of prior service cost/(credit)		(3)		(2)		(5)		(5)
Amortization of unrecognized loss		1		-		1		1
Net periodic postretirement benefit cost	$	13	$	13	$	26	$	21