Pension Plan Contributions (Details) - Pension Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Multiemployer Plans [Line Items]
Multiemployer Plan, Employer Contribution, Cost	$ 929	$ 2,063	$ 2,642
Multiemployer Plan Year Allocation Four [Member]
Multiemployer Plans [Line Items]
Multiemployer Plan, Employer Contribution, Cost			2,000
Multiemployer Plan Year Allocation One [Member]
Multiemployer Plans [Line Items]
Multiemployer Plan, Employer Contribution, Cost	$ 929
Multiemployer Plan Year Allocation Two [Member]
Multiemployer Plans [Line Items]
Multiemployer Plan, Employer Contribution, Cost		$ 2,063
Multiemployer Plan Year Allocation Three [Member]
Multiemployer Plans [Line Items]
Multiemployer Plan, Employer Contribution, Cost			$ 642