Pension and Other Post-Retirement Benefits

The following table shows the components of our pension and other post-retirement benefits expense for the three months ended September 30, 2018 and 2017 (in millions):



	2018 Pension Benefits			2017 Pension Benefits			2018 Retiree Health and Life			2017 Retiree Health and Life
Service cost	$	2.0		$	1.6		$	0.1		$	—
Interest cost	3.7			3.8			0.2			0.2
Expected return on plan assets	(5.6		)	(5.9		)	—			—
Settlement expense	2.1			—			—			—
Amortization of (1):
Unrecognized prior service credit	—			—			(0.1		)	—
Unrecognized net actuarial loss	2.5			2.2			—			—
Net periodic cost	$	4.7		$	1.7		$	0.2		$	0.2

The following table shows the components of our pension and other post-retirement benefits expense for the nine months ended September 30, 2018 and 2017 (in millions):



	2018 Pension Benefits			2017 Pension Benefits			2018 Retiree Health and Life			2017 Retiree Health and Life
Service cost	$	6.1		$	4.9		$	0.2		$	0.1
Interest cost	11.1			11.5			0.7			0.7
Expected return on plan assets	(16.7		)	(17.9		)	—			—
Settlement expense	2.1			0.1			—			—
Amortization of (1):
Unrecognized prior service credit	—			—			(0.2		)	(0.1		)
Unrecognized net actuarial loss (gain)	7.6			6.9			—			(0.2		)
Net periodic cost	$	10.2		$	5.5		$	0.7		$	0.5

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(1) Amounts reclassified from accumulated other comprehensive loss.

In 2018, we adopted ASU 2017-07 which modifies how an entity must present service costs and other components of net benefit cost. See "Note 2. Basis of Presentation" for further details. In accordance with this new guidance, the service cost component of net periodic cost is recorded in the applicable operating expense line, including maintenance expense and selling, general and administrative expense in the Statements of Comprehensive Income; and the other components are recorded in other expense.

During the third quarter of 2018, we recorded a settlement accounting expense of $2.1 million attributable to certain lump-sum distributions made during the period.