Pension Plans - Qualified Plan - Allocation of Defined Benefit Pension Plans Assets (Details) - Pension Plan [Member] - Qualified Plan [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Information about Plan Assets [Abstract]
Plan assets	$ 59,653	$ 69,245	$ 65,446
Defined Benefit Plan, Cash [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Plan assets	162	642
Mutual Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Plan assets	$ 59,491	$ 68,603