Retirement Benefit Plans

9 Months Ended

Mar. 31, 2019

8. Retirement Benefit Plans

We sponsor various retirement benefit plans including qualified and nonqualified defined benefit pension plans for our employees. The components of net periodic pension expense are as follows (in thousands):


	Three Months Ended March 31,				Nine Months Ended March 31,
	2018		2019		2018		2019
Service cost	$	216	$	98	$	648	$	295
Interest cost		9		8		25		25
Amortization of prior service cost		70		14		210		42
Net periodic pension expense	$	295	$	120	$	883	$	362

For each of the three months ended March 31, 2018 and 2019, we made no contributions to these defined benefit plans. For each of the nine months ended March 31, 2018 and 2019, we made contributions of $1.0 million to these defined benefit plans.

We also maintain various defined contribution plans. For each of the three months ended March 31, 2018 and 2019, we made contributions of $1.6 million to these defined contribution plans. For the nine months ended March 31, 2018 and 2019, we made contributions of $4.6 million and $4.7 million, respectively, to these defined contribution plans.