Retirement Benefits - Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2020 employee
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer	$ 1,100
Participants affected due to plan freeze (fewer than) | employee			60
Funded percentage	113.00%
Defined benefit plan, assets	$ 88,100
Defined benefit plan, liability	77,800
Other (Income) Expense Net
Defined Benefit Plan Disclosure [Line Items]
Settlement loss recognized	48	$ 300
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