Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2020

Retirement Benefits [Abstract]

Company's pension and postretirement benefit plans

Components of net cost (benefit) for pension and other postretirement plans
	Three months ended June 30,						Six months ended June 30,
($ in millions)	2020			2019			2020			2019
Pension benefits
Service cost	$	25		$	28		$	53		$	56
Interest cost	56			62			112			127
Expected return on plan assets	(95		)	(101		)	(199		)	(194		)
Amortization of prior service credit	(14		)	(14		)	(28		)	(28		)
Costs and expenses	(28		)	(25		)	(62		)	(39		)
Remeasurement of projected benefit obligation	672			344			556			731
Remeasurement of plan assets	(623		)	(225		)	(189		)	(616		)
Remeasurement (gains) losses	49			119			367			115
Pension net cost	$	21		$	94		$	305		$	76
Postretirement benefits
Service cost	$	2		$	2		$	3		$	4
Interest cost	3			3			6			7
Amortization of prior service credit	(1		)	(1		)	(2		)	(2		)
Costs and expenses	4			4			7			9
Remeasurement of projected benefit obligation	24			6			24			25
Remeasurement of plan assets	—			—			—			—
Remeasurement (gains) losses	24			6			24			25
Postretirement net cost	$	28		$	10		$	31		$	34
Pension and postretirement benefits
Costs and expenses	$	(24	)	$	(21	)	$	(55	)	$	(30	)
Remeasurement (gains) losses	73			125			391			140
Total net cost	$	49		$	104		$	336		$	110

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 postretirement benefits remeasurement gains and losses
	Three months ended June 30,						Six months ended June 30,
($ in millions)	2020			2019			2020			2019
Remeasurement of projected benefit obligation (gains) losses:
Discount rate	$	433		$	228		$	397		$	493
Other assumptions	263			122			183			263
Remeasurement of plan assets (gains) losses	(623		)	(225		)	(189		)	(616		)
Remeasurement (gains) losses	$	73		$	125		$	391		$	140