6. Pension plans and other postretirement benefits

The Company provides defined benefit pension and other postretirement benefits (including health care and life insurance benefits) to qualified retired employees. Net periodic defined benefit cost for defined benefit plans consisted of the following:

	Pension Benefits						Other Postretirement Benefits
	Three Months Ended June 30
	2018			2017			2018			2017
	(In thousands)

Service cost	$	5,069			5,189			243		202
Interest cost on projected benefit obligation		18,548			19,943			589			778
Expected return on plan assets		(30,688	)		(27,062	)		—			—
Amortization of prior service cost (credit)		153			154			(1,189	)		(329	)
Amortization of net actuarial loss (gain)		10,796			7,831			(213	)		(469	)
Net periodic benefit cost	$	3,878			6,055			(570	)		182

	Pension Benefits						Other Postretirement Benefits
	Six Months Ended June 30
	2018			2017			2018			2017
	(In thousands)

Service cost	$	10,172			10,097			469			585
Interest cost on projected benefit obligation		37,353			39,634			1,146			1,858
Expected return on plan assets		(61,563	)		(54,262	)		—			—
Amortization of prior service cost (credit)		278			279			(2,364	)		(679	)
Amortization of net actuarial loss (gain)		21,896			14,631			(413	)		(494	)
Net periodic benefit cost	$	8,136			10,379			(1,162	)		1,270

Service cost is reflected in salaries and employee benefits expense. The other components of net periodic benefit cost are reflected in other costs of operations. Expenses incurred in connection with the Company's defined contribution pension and retirement savings plans totaled $17,194,000 and $17,623,000 for the three months ended June 30, 2018 and 2017, respectively, and $38,468,000 and $37,042,000 for the six months ended June 30, 2018 and 2017, respectively, and are included in salaries and employee benefits expense.