Employee Benefits

Net periodic benefit (income) expense for our combined pension plan includes the following components:



	Combined Pension Plan
	Three Months Ended March 31,
	2019			2018
	(Dollars in millions)
Service cost	$	14		16
Interest cost	110			100
Expected return on plan assets	(156		)	(173	)
Recognition of prior service credit	(2		)	(2	)
Recognition of actuarial loss	57			44
Net periodic pension benefit expense (income)	$	23		(15	)

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



	Post-Retirement Benefit Plans
	Three Months Ended March 31,
	2019		2018
	(Dollars in millions)
Service cost	$	4	4
Interest cost	27		24
Recognition of prior service cost	4		5
Net periodic post-retirement benefit expense	$	35	33

Service costs are included in the cost of services and products and selling, general and administrative line items on the Statement of Operations and all other costs listed above are included in the other (expense) income, net line item on the Statement of Operations. Benefits paid by our qualified pension plan are paid through a trust that holds all of the plan's assets. Based on current laws and circumstances, we do not expect any contributions to be required for our qualified pension plan during 2019. The amount of required contributions to our qualified pension plan in 2020 and beyond will depend on a variety of factors, most of which are beyond our control, including earnings on plan investments, prevailing interest rates, demographic experience, changes in plan benefits and changes in funding laws and regulations. We occasionally make voluntary contributions in addition to required contributions. Based on current circumstances, we do not anticipate making a voluntary contribution to the trust for our qualified pension plan in 2019.