Retirement Benefit Plans

6 Months Ended

Dec. 31, 2018

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 December 31,				Six Months Ended December 31,
	2017		2018		2017		2018
Service cost	$	216	$	98	$	432	$	196
Interest cost		8		8		16		16
Amortization of prior service cost		70		14		140		28
Net periodic pension expense	$	294	$	120	$	588	$	240

For the three months ended December 31, 2017, we made no contributions to these defined benefit plans. For the three months ended December 31, 2018, we made contributions of $1.0 million to these defined benefit plans. For each of the six months ended December 31, 2017 and 2018, we made contributions of $1.0 million to these defined benefit plans.

We also maintain various defined contribution plans. For the three months ended December 31, 2017 and 2018, we made contributions of $1.4 million and $1.3 million , respectively, to these defined contribution plans. For the six months ended December 31, 2017 and 2018, we made contributions of $3.0 million and $3.1 million, respectively, to these defined contribution plans.