The Company has defined contribution retirement plans or defined benefit pension plans covering substantially all employees. Company contributions to defined contribution retirement plans are generally based on a percentage of eligible pay or based on hours worked. Benefits under the defined benefit pension plans are generally based on years of service and/or final average pay. The Company funds the U.S. pension plans in accordance with the Employee Retirement Income Security Act of 1974, as amended, and the Internal Revenue Code.

The Company also sponsors several postretirement plans covering certain collectively-bargained salaried and hourly employees. The plans provide health care and life insurance benefits for eligible retirees. In most retiree health care plans, Company contributions towards premiums are capped based on the cost as of a certain date, thereby creating a defined contribution.

For the three month periods ended June 30, 2017 and 2016, the components of pension and other postretirement benefit expense for the Company’s defined benefit plans included the following (in millions):



	Pension Benefits						Other Postretirement Benefits
	Three months ended June 30,						Three months ended June 30,
	2017			2016			2017			2016
Service cost - benefits earned during the year	$	3.5		$	5.1		$	0.6		$	0.7
Interest cost on benefits earned in prior years	29.2			31.3			3.6			3.9
Expected return on plan assets	(36.7		)	(37.1		)	—			—
Amortization of prior service cost (credit)	0.3			0.3			(0.7		)	(0.8		)
Amortization of net actuarial loss	15.7			16.4			2.3			2.4
Total retirement benefit expense	$	12.0		$	16.0		$	5.8		$	6.2

For the six month periods ended June 30, 2017 and 2016, the components of pension and other postretirement benefit expense for the Company’s defined benefit plans included the following (in millions):



	Pension Benefits						Other Postretirement Benefits
	Six months ended June 30,						Six months ended June 30,
	2017			2016			2017			2016
Service cost - benefits earned during the year	$	7.0		$	10.3		$	1.2		$	1.3
Interest cost on benefits earned in prior years	58.4			62.7			7.3			8.0
Expected return on plan assets	(73.4		)	(74.3		)	—			—
Amortization of prior service cost (credit)	0.6			0.6			(1.4		)	(0.2		)
Amortization of net actuarial loss	31.3			32.7			4.5			4.8
Total retirement benefit expense	$	23.9		$	32.0		$	11.6		$	13.9

Effective January 31, 2017, closure of the U.K. defined benefit pension plan to future accruals for service and pay (hard freeze) occurred. In March 2017, the Company made a $135 million cash contribution to the ATI Pension Plan, its U.S. qualified defined benefit pension plan, completing the Company’s funding requirements for 2017.