Retirement Plans (Tables)

3 Months Ended

Mar. 31, 2019

Retirement Plans [Abstract]

Net Periodic Benefit Cost

	Pension Benefits
	For the three months ended
	March 31,
($ in millions)	2019		2018
Components of total pension benefit cost
Service cost	$	21	$	24
Interest cost on projected benefit obligation		33		30
Expected return on plan assets		(43)		(50)
Amortization of unrecognized loss		14		7
Net periodic pension benefit cost	$	25	$	11
	Postretirement Benefits
	For the three months ended
	March 31,
($ in millions)	2019		2018
Components of net periodic postretirement benefit cost
Service cost	$	5	$	5
Interest cost on projected benefit obligation		10		9
Amortization of prior service cost (credit)		(1)		(2)
Amortization of unrecognized (gain) loss		(2)		1
Net periodic postretirement benefit cost	$	12	$	13