We have a defined benefit pension plan (pension plan) that covers certain U.S. citizen employees and other employees who are permanent residents of the United States. The Board of Directors amended the pension plan to discontinue the accrual of benefits once the plan was frozen on December 31, 2010. We contributed $1.1 million to the pension plan during the nine months ended September 30, 2019.

We also support a non-contributory and non-qualified defined benefit supplemental executive retirement plan (supplemental plan) that provided pension benefits to certain employees in excess of those allowed under our tax-qualified pension plan. Effective March 4, 2010, the supplemental plan was closed to new participants. We contributed $2.1 million and $2.9 million during the three and nine months ended September 30, 2019, respectively. We contributed immaterial amounts to the supplemental plan during the three and nine months ended September 30, 2018. We expect to contribute $0.4 million to the supplemental plan during the remaining quarter of 2019. Our obligations under the supplemental plan were $19.3 million and $21.4 million as of September 30, 2019 and December 31, 2018, respectively, and are included in “accrued costs and expenses” and “other liabilities” on the consolidated balance sheet.

We also have defined benefit pension plans that cover certain Norwegian citizen employees and other employees who are permanent residents of Norway. Benefits are based on years of service and employee compensation. We contributed an immaterial amount to the Norwegian defined benefit pension plans during the three and nine months ended September 30, 2019 and 2018 and contributions during the remainder of calendar year 2019 are expected to be immaterial.

The net periodic benefit cost for our defined benefit pension plans and supplemental plan (referred to collectively as “Pension Benefits”) is comprised of the following components:

	Three Months Ended						Nine Months Ended
(In thousands)	September 30, 2019			September 30, 2018			September 30, 2019			September 30, 2018
Pension Benefits:
Service cost	$	316			47			328			118
Interest cost		1,006			872			2,853			2,656
Expected return on plan assets		(711	)		(481	)		(1,787	)		(1,446	)
Administrative expenses		83			3			90			6
Settlement loss recognized		(46	)		—			46			335
Net periodic pension cost	$	648			441		$	1,530			1,669