Retirement Benefits - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Mar. 31, 2020 employee
Defined Benefit Plan Disclosure [Line Items]
Contributions by employer			$ 3,000
Participants affected due to plan freeze (fewer than) | employee					60
Funded percentage	110.00%		110.00%
Defined benefit plan, assets	$ 93,400		$ 93,400
Defined benefit plan, liability	84,800		84,800
Other (Income) Expense Net
Defined Benefit Plan Disclosure [Line Items]
Settlement loss recognized		$ 500	700	$ 500
Reduction in net periodic benefit cost			1,000
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected contribution for next fiscal year	3,000		3,000
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected contribution for next fiscal year		1,100		1,100
Reduction in net periodic benefit cost	$ (175)	$ (194)	$ (525)	$ (581)