Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2021

Retirement Benefits [Abstract]

Company's pension and postretirement benefit plans

Components of net cost (benefit) for pension and other postretirement plans
	Three months ended September 30,				Nine months ended September 30,
($ in millions)	2021		2020		2021		2020
Pension benefits
Service cost	$	27	$	25	$	78	$	78
Interest cost	47		49		145		161
Expected return on plan assets	(112)		(104)		(338)		(303)
Amortization of prior service credit	(13)		(14)		(38)		(42)
Curtailment loss	—		10		—		10
Costs and expenses	(51)		(34)		(153)		(96)
Remeasurement of projected benefit obligation	(25)		130		(292)		686
Remeasurement of plan assets	68		(202)		(99)		(391)
Remeasurement (gains) losses	43		(72)		(391)		295
Pension net (benefit) cost	$	(8)	$	(106)	$	(544)	$	199
Postretirement benefits
Service cost	$	—	$	1	$	1	$	4
Interest cost	2		2		6		8
Amortization of prior service credit	(5)		(1)		(18)		(3)
Curtailment gain	—		(8)		—		(8)
Costs and expenses	(3)		(6)		(11)		1
Remeasurement of projected benefit obligation	(3)		1		(13)		25
Remeasurement of plan assets	—		—		—		—
Remeasurement (gains) losses	(3)		1		(13)		25
Postretirement net (benefit) cost	$	(6)	$	(5)	$	(24)	$	26
Pension and postretirement benefits
Costs and expenses	$	(54)	$	(40)	$	(164)	$	(95)
Remeasurement (gains) losses	40		(71)		(404)		320
Total net (benefit) cost	$	(14)	$	(111)	$	(568)	$	225

Differences between expected and actual returns on plan assets and changes in assumptions affect the Company’s pension and other postretirement obligations, plan assets and expenses.

Pension and other postretirement service cost, interest cost, expected return on plan assets, amortization of prior service credit and curtailment gains and losses are reported in property and casualty insurance claims and claims expense, operating costs and expenses, net investment income and (if applicable) restructuring and related charges on the Condensed Consolidated Statement of Operations.

Pension and postretirement benefits remeasurement gains and losses
	Three months ended September 30,				Nine months ended September 30,
($ in millions)	2021		2020		2021		2020
Remeasurement of projected benefit obligation (gains) losses:
Discount rate	$	(32)	$	57	$	(271)	$	454
Other assumptions	4		74		(34)		257
Remeasurement of plan assets (gains) losses	68		(202)		(99)		(391)
Remeasurement (gains) losses	$	40	$	(71)	$	(404)	$	320