Defined Benefit Pension Plans Funded status of the plans (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	$ 3,758	$ 7,105	$ 11,509
Projected benefit obligation	7,064	19,403	$ 24,833
Funded status of the plans	(3,306)	(12,298)
Defined Benefit Plan, Plan Name ERP Funded Status	(332)	(9,084)
Defined Benefit Plan, Plan Name SERP Funded Status	(2,564)	(2,759)
Defined Benefit Plan, Plan Name Restoration Plan Funded Status	$ (410)	$ (455)