Retirement Benefits - Narrative (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2016 USD ($) benefit_plan	Dec. 31, 2017 USD ($) benefit_plan	Dec. 31, 2016 USD ($) benefit_plan	Dec. 31, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 876,200,000	$ 924,600,000	$ 876,200,000
Number of defined contribution pension plans (benefit plan) | benefit_plan		6
Defined contribution pension plans, total costs		$ 19,800,000	$ 15,600,000	$ 13,300,000
Number of multiemployer defined benefit pension plans (benefit_plan) | benefit_plan	2		2
Number of multiemployer plans withdrawn from | benefit_plan		1
Multiemployer plan total employer contributions		$ 400,000	$ 500,000	800,000
Pre-tax restructuring costs		20,300,000	35,000,000	23,600,000
Expected cost remaining		4,000,000
Employer stock included in plan assets	$ 40,000,000	0	$ 40,000,000
Employer stock as percentage of plan assets	6.60%		6.60%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit)		100,000	$ 100,000	200,000
Benefit obligation	$ 917,400,000	$ 956,100,000	$ 917,400,000	$ 912,300,000
Discount rate	4.12%	3.67%	4.12%	4.71%
Employer contributions		$ 9,800,000	$ 24,300,000
Withdrawal from Multiemployer Defined Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Pre-tax restructuring costs	$ 12,500,000
Expected cost remaining		$ 23,000,000
U.S. Defined Benefit Pension Plan | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Curtailment gain			34,100,000
Amortization of prior service cost (credit)			200,000
Projected benefit obligation settled			$ 40,000,000
Voluntary lump sum program payment				$ 27,700,000
Defined benefit obligation per plan, as a percent of total benefit obligation		88.00%
Discount rate	4.30%	3.80%	4.30%
Effect on defined benefit obligation, due to change in mortality table utilized		$ 15,000,000
Estimated future employer contributions in next fiscal year		$ 1,900,000
Foreign Plan | Canada
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.85%	3.50%	3.85%
Foreign Plan | United Kingdom
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.70%	2.60%	2.70%