Retirement Benefits - Narrative (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) employee shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2020 employee
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, funded percentage			113.00%
Other noncurrent assets			$ 93,400
Liability, defined benefit plan			82,600
Accumulated benefit obligation for all defined benefit pension plans		$ 193,300	$ 204,400	$ 193,300
Percentage of excess gains and losses over benefit obligation or market value of assets amortized			10.00%
Costs of defined contribution plans			$ 12,500	12,400	$ 12,200
Number of participants covering under multi employer pension plan | employee			305
Costs of bargaining unit-sponsored multi-employer plans and defined contribution plans			$ 1,100	1,100	1,100
Weighted average annual rate of increase in the per capita cost of covered health care benefits assumed			5.64%
Assumed decrease of weighted average health care cost trend rate			4.50%
Year that reaches assumed decrease of weighted average health care cost trend rate			2038
Stock held in plan assets (in shares) | shares			0
Estimated Future Benefit Payments
2021			$ 88,500
2022			5,900
2023			5,900
2024			6,100
2025			6,300
2026 to 2030			32,300
Other (Income) Expense Net
Defined Benefit Plan Disclosure [Line Items]
Settlement loss recognized	$ 900	700
Net periodic benefit cost			1,000
Defined Contribution Plan
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, expected contribution for next fiscal year			13,100
401k
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, expected contribution for next fiscal year			$ 10,100
U.S. | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation of fund assets in equities			10.00%
U.S. | Fixed Income Securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation of fund assets in equities			90.00%
UK | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation of fund assets in equities			60.00%
UK | Equity Securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation of fund assets in equities			50.00%
UK | Equity Securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation of fund assets in equities			60.00%
UK | Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation of fund assets in equities			40.00%
UK | Fixed Income Securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation of fund assets in equities			40.00%
UK | Fixed Income Securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation of fund assets in equities			50.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Participants affected due to plan freeze | employee						60
Defined benefit plan, expected contribution for next fiscal year			$ 3,400
Pension Benefits | U.S.
Defined Benefit Plan Disclosure [Line Items]
Settlement loss recognized			910	713	(1)
Net periodic benefit cost			269	(2,733)	(2,288)
Other noncurrent assets		1,921	10,754	1,921
Pension Benefits | Non-U.S.
Defined Benefit Plan Disclosure [Line Items]
Settlement loss recognized			(385)	0	(307)
Net periodic benefit cost			(3,446)	(3,354)	(3,338)
Other noncurrent assets		14	$ 3	14
Pension Benefits | UK
Defined Benefit Plan Disclosure [Line Items]
Target allocation of fund assets in equities			2.50%
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost			$ (698)	(775)	$ (741)
Other noncurrent assets		$ 0	0	$ 0
Defined benefit plan, expected contribution for next fiscal year			$ 1,000