9. Pension Plans

The company has both tax-qualified and nonqualified, noncontributory defined benefit pension plans, that together cover certain domestic and foreign employees. These plans provide benefits based upon a participant’s compensation and years of service.

The components of net periodic pension cost are as follows:


	Quarter Ended September 30,						Nine Months Ended September 30,
	2016			2015			2016			2015
(dollars in millions)
Service cost, net of employee contributions	$	7.5		$	7.1		$	22.0		$	22.1
Interest cost		4.8			5.2			14.2			15.1
Expected return on plan assets		(8.0	)		(7.9	)		(24.2	)		(23.5	)
Amortization		2.6			3.1			7.8			8.9

Net periodic pension cost	$	6.9		$	7.5		$	19.8		$	22.6

In 2016, the company changed its method used to estimate the service and interest cost components of net periodic benefit cost for defined benefit plans from a single weighted-average discount rate to a full yield curve approach. The reduction in service and interest cost for the quarter and nine months ended September 30, 2016 associated with this change in estimate was approximately $1.2 million and $3.8 million, respectively.