Retirement plans

Our principal defined benefit pension plan is the TEGNA Retirement Plan (TRP). The disclosure table below includes the pension expenses of the TRP and the Supplemental Retirement Plan (SERP). In connection with our acquisition of KFMB, we assumed its preexisting pension plan which, as of the acquisition date, had a total net pension obligation of $7.3 million. All plan participants’ benefits were frozen prior to the acquisition date. During the second quarter of 2018, the KFMB pension plan was merged into the TRP. The total net pension obligations, both current and non-current liabilities, as of June 30, 2018, were $142.1 million ($5.1 million is recorded as a current obligation within accrued liabilities on the Condensed Consolidated Balance Sheet).

Our pension costs, which primarily include costs for the qualified TRP and the non-qualified SERP plan, are presented in the following table (in thousands):



	Quarter ended June 30,						Six months ended June 30,
	2018			2017			2018			2017

Service cost-benefits earned during the period	$	6		$	311		$	6		$	436
Interest cost on benefit obligation	5,074			6,056			10,224			11,981
Expected return on plan assets	(7,480		)	(6,511		)	(14,930		)	(13,161		)
Amortization of prior service cost	34			167			84			317
Amortization of actuarial loss	1,293			2,187			2,543			4,162
Lump-sum payment charge	—			—			6,300			—
Expense for company-sponsored retirement plans	$	(1,073	)	$	2,210		$	4,227		$	3,735

The service cost component of our pension expense is recorded within the operating expense line items Cost of revenue, Business units - Selling, general and administrative, and Corporate - General and administrative within the Consolidated Statements of Income. All other components of the pension expense are included within the Other non-operating items line item of the Consolidated Statements of Income.

During the six months ended June 30, 2018 we made $6.4 million in cash contributions to the TRP, and plan to make additional contributions of $4.7 million to the TRP during the remainder of 2018. We made $1.7 million in cash contributions to the TRP during the six months ended June 30, 2017. During the six months ended June 30, 2018 and 2017, we made benefit payments to participants of the SERP of $28.8 million and $3.8 million, respectively.

In the first quarter of 2018, we incurred a special charge as a result of the lump sum payments under the SERP plan. This charge of $6.3 million was reclassified from accumulated other comprehensive income (loss) into net periodic benefit cost.