7. Retirement Plans

Components of net pension and other postretirement benefits plan (“OPEB”) income for the three and nine months ended September 30, 2018 and 2017 were as follows:

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2018			2017			2018			2017
Pension expense (income):
Service cost	$	0.1		$	0.1		$	0.5		$	0.5
Interest cost		7.7			8.0			23.4			23.7
Expected return on plan assets		(12.4	)		(12.7	)		(37.6	)		(37.6	)
Amortization, net		2.0			1.9			5.9			5.4
Settlements		0.2			—			1.5			—
Net pension income	$	(2.4	)	$	(2.7	)	$	(6.3	)	$	(8.0	)

OPEB expense (income):
Service cost	$	(0.3	)	$	0.4		$	0.5		$	1.0
Interest cost		2.5			2.7			7.7			8.3
Expected return on plan assets		(3.5	)		(3.4	)		(10.5	)		(10.1	)
Amortization, net		(0.8	)		(0.7	)		(2.2	)		(2.2	)
Other		(5.1	)		—			(5.1	)		—
Net other postretirement benefit income	$	(7.2	)	$	(1.0	)	$	(9.6	)	$	(3.0	)

During the nine months ended September 30, 2018, we contributed $13.5 million to our retirement plans.

Other OPEB income during the three and nine months ended September 30, 2018 reflects the change in one of our OPEB liabilities due to a revision to participant demographic data utilized in the actuarial valuations.

We adopted ASU No. 2017-07 “Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost”, with retrospective adoption, during the first quarter of 2018. In accordance with Topic 715, benefit service cost is recorded in cost of sales and selling, general and administrative expenses. The other components, which include interest cost, expected return on plan assets, net amortization and settlements, are recorded in Investment and other income-net within the Condensed Consolidated Statements of Operations. Previously, all pension and postretirement benefits expense (income) was recorded in cost of sales and selling, general and administrative expenses. See Note 17, New Accounting Pronouncements, for further discussion and impact of adoption.