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 September 30
	2018			2017			2018			2017
	(In thousands)

Service cost	$	5,086			5,048			234		293
Interest cost on projected benefit obligation		18,676			19,818			573			929
Expected return on plan assets		(30,781	)		(27,131	)		—			—
Amortization of prior service cost (credit)		139			139			(1,182	)		(340	)
Amortization of net actuarial loss (gain)		10,948			7,316			(206	)		(247	)
Net periodic benefit cost	$	4,068			5,190			(581	)		635

	Pension Benefits						Other Postretirement Benefits
	Nine Months Ended September 30
	2018			2017			2018			2017
	(In thousands)

Service cost	$	15,258			15,145			703			878
Interest cost on projected benefit obligation		56,029			59,452			1,719			2,787
Expected return on plan assets		(92,344	)		(81,393	)		—			—
Amortization of prior service cost (credit)		417			418			(3,546	)		(1,019	)
Amortization of net actuarial loss (gain)		32,844			21,947			(619	)		(741	)
Net periodic benefit cost	$	12,204			15,569			(1,743	)		1,905

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 $16,907,000 and $16,085,000 for the three months ended September 30, 2018 and 2017, respectively, and $55,375,000 and $53,127,000 for the nine months ended September 30, 2018 and 2017, respectively, and are included in salaries and employee benefits expense.