Retirement Benefits - Funded Status and Components of Post Retirement Benefit Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefits paid	$ (103)	$ (120)	$ (112)
Other Pension Plans, Defined Benefit
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Accumulated postretirement benefit obligation beginning of year	1,359	1,645	1,697
Service cost	9	11	11
Interest cost	52	52	57
Actuarial (gain) loss	(76)	(229)	(8)
Benefits paid	(103)	(120)	(112)
Accumulated postretirement benefit obligation end of year	1,241	1,359	1,645
Accrued liability (included in accrued expenses and other liabilities)	$ 1,241	$ 1,359	$ 1,645