Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2015

Compensation and Retirement Disclosure [Abstract]

Company's pension and postretirement benefit plans

The components of net periodic cost for the Company’s pension and postretirement benefit plans are as follows:

($ in millions)	Three months ended March 31,
	2015			2014
Pension benefits
Service cost	$	29		$	24
Interest cost	64			64
Expected return on plan assets	(106		)	(99		)
Amortization of:
Prior service credit	(14		)	(15		)
Net actuarial loss	48			29
Settlement loss	6			11
Net periodic pension cost	$	27		$	14
Postretirement benefits
Service cost	$	3		$	3
Interest cost	6			6
Amortization of:
Prior service credit	(6		)	(6		)
Net actuarial gain	(2		)	(6		)
Net periodic postretirement cost (credit)	$	1		$	(3	)