Employee Benefit Plans

3 Months Ended

Mar. 31, 2016

Compensation and Retirement Disclosure [Abstract]

Employee Benefit Plans

Employee Benefit Plans

We have defined benefit pension plans for our U.K.-based union employees (the "U.K. Plan") and certain Canadian-based employees (the "Canadian Plan"). Retirement benefits under the U.K. Plan are generally based on an employee's average compensation over the two years preceding retirement. Retirement benefits under the Canadian Plan are generally based on the number of years of credited service. Our policy is to fund the minimum contribution permissible by the applicable authorities. See Note 19 (Pension and Other Post Retirement Plans) in our 2015 Annual Report on Form 10-K.

Our pension benefit costs are calculated using various actuarial assumptions and methodologies. These assumptions include discount rates, inflation, compensation increase rates, expected returns on plan assets, mortality rates and other factors. The assumptions utilized in recording the obligations under our plans represent our best estimates, and we believe that they are reasonable, based on information as to historical experience and performance as well as other factors that might cause future expectations to differ from past trends. Differences in actual experience or changes in assumptions may affect our pension obligations and future expense. The primary factors contributing to actuarial gains and losses each year are (1) changes in the discount rate used to value pension benefit obligations as of the measurement date and (2) differences between the expected and the actual return on plan assets.

The following table sets forth the combined amount of net periodic benefit cost recognized for the three months ended March 31, 2016 and 2015:

	Three Months Ended   March 31,
	2016			2015
Components of net periodic pension benefit cost:
Service cost	$	0.6		$	0.7
Interest cost	1.2			1.2
Expected return on plan assets	(1.6		)	(1.7		)
Amortization of actuarial losses	0.2			0.3
Amortization of unrecognized prior service cost	(0.1		)	—
Net periodic cost	$	0.3		$	0.5

We have a 401(k) plan for U.S.-based employees. Those employees who participate in our 401(k) plan are eligible to receive matching contributions of 35% from us for participant contributions up to the first 6% of their compensation (as defined in the plan document). Contribution expense for the three months ended March 31, 2016 and 2015 was $2.9 million and $3.1 million, respectively.