Retirement Benefits - Narrative (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Sep. 30, 2019 employee
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	$ 2,200
Participants affected due to plan freeze (fewer than) | employee			60
Termination of the U.S. pension plan	9,688	$ 0
Previously deferred pension cost	10,700
Increase in plan assets	1,000
Funded status of plan	11,200
Other (Income) Expense Net
Defined Benefit Plan Disclosure [Line Items]
Termination of the U.S. pension plan	9,700
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected contribution for next fiscal year	3,400
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected contribution for next fiscal year	$ 1,000