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 TEGNA Supplemental Retirement Plan (SERP). The total net pension obligations, including both current and non-current liabilities, as of March 31, 2019, were $145.5 million ($7.9 million is recorded as a current obligation within accrued liabilities on the Condensed Consolidated Balance Sheet).

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



	Quarter ended Mar. 31,
	2019			2018

Interest cost on benefit obligation	$	5,750		$	5,150
Expected return on plan assets	(6,575		)	(7,450		)
Amortization of prior service cost	25			50
Amortization of actuarial loss	1,500			1,250
Pension payment timing related charge	—			6,300
Expense for company-sponsored retirement plans	$	700		$	5,300

Our TRP and SERP plans are frozen plans, and as such we no longer incur the service cost component of pension expense. All other components of our pension expense presented above are included within the Other non-operating items line item of the Consolidated Statements of Income.

During the three months ended March 31, 2019 we made no cash contributions to the TRP and made $1.7 million in cash contributions to the TRP during the three months ended March 31, 2018. During the three months ended March 31, 2019 and 2018, we made benefit payments to participants of the SERP of $0.9 million and $26.7 million, respectively. SERP payments during the three months ended March 31, 2018 primarily related to lump sum payments made to certain former executives of the company. Based on actuarial projections, we expect to make additional cash payments of $10.7 million in 2019 on account of these benefit plans (comprised of payments of $6.9 million to SERP participants and $3.8 million of contributions to the TRP).

In the first quarter of 2018, we incurred a pension payment timing related charge of $6.3 million as a result of lump sum SERP payments made to certain former executives. The 2018 charge was reclassified from accumulated other comprehensive income into net periodic benefit cost.