Employee Benefits (Tables)

6 Months Ended

Jun. 30, 2018

Retirement Benefits [Abstract]

Schedule of components of net periodic pension benefit (income) expense and post-retirement benefit expense

Net periodic benefit (income) expense for our qualified and non-qualified pension plans included the following components:

	Pension Plans
	Three Months Ended June 30,					Six Months Ended June 30,
	2018			2017		2018		2017
	(Dollars in millions)
Service cost	$	16		14		32		31
Interest cost	98			105		197		206
Expected return on plan assets	(171		)	(167	)	(342	)	(333	)
Recognition of prior service credit	(2		)	(2	)	(4	)	(4	)
Recognition of actuarial loss	46			52		90		103
Net periodic pension benefit (income) expense	$	(13	)	2		(27	)	3

Net periodic benefit expense for our post-retirement benefit plans included the following components:

	Post-Retirement Benefit Plans
	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018	2017
	(Dollars in millions)
Service cost	$	5	5		9	9
Interest cost	25		25		49	50
Expected return on plan assets	—		(1	)	—	(1	)
Recognition of prior service cost	5		5		10	10
Net periodic post-retirement benefit expense	$	35	34		68	68