Retirement Benefits (Unaudited) (Tables)

6 Months Ended

Jun. 30, 2017

Compensation and Retirement Disclosure [Abstract]

Components of net periodic benefit cost

The cost to the company of its retirement plans is shown in the following table:

	Three Months Ended June 30												Six Months Ended June 30
	Pension Benefits						Medical and Life Benefits						Pension Benefits						Medical and Life Benefits
$ in millions	2017			2016			2017			2016			2017			2016			2017			2016
Components of net periodic benefit cost
Service cost	$	114		$	111		$	7		$	7		$	228		$	223		$	13		$	15
Interest cost	308			321			21			23			617			642			42			47
Expected return on plan assets	(472		)	(463		)	(23		)	(22		)	(943		)	(926		)	(45		)	(43		)
Amortization of:
Prior service credit	(14		)	(15		)	(6		)	(5		)	(29		)	(30		)	(11		)	(11		)
Net loss from previous years	178			179			3			5			356			357			5			8
Net periodic benefit cost	$	114		$	133		$	2		$	8		$	229		$	266		$	4		$	16

Employer contributions to retirement plans

Contributions made by the company to its retirement plans are as follows:

	Three Months Ended June 30				Six Months Ended June 30
$ in millions	2017		2016		2017		2016
Defined benefit pension plans	$	28	$	20	$	51	$	47
Medical and life benefit plans	13		18		24		29
Defined contribution plans	77		71		176		158