Pension Plans - Qualified Plan - Allocation of Defined Benefit Pension Plans Assets (Details) - Pension Plan [Member] - Qualified Plan [Member] - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Information about Plan Assets [Abstract]
Plan assets	$ 71,221	$ 66,000	$ 59,653
Defined Benefit Plan, Cash [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Plan assets	2,457	43
Mutual Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Plan assets	$ 68,764	$ 65,957