Pension Plan Contributions (Details) - Pension Plan [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Multiemployer Plans [Line Items]
Cash payment	$ 2,642	$ 6,432	$ 6,245
Multiemployer Plan Year Allocation Four [Member]
Multiemployer Plans [Line Items]
Cash payment	2,000	5,000	4,000
Multiemployer Plan Year Allocation One [Member]
Multiemployer Plans [Line Items]
Cash payment	$ 642
Multiemployer Plan Year Allocation Two [Member]
Multiemployer Plans [Line Items]
Cash payment		$ 1,432
Multiemployer Plan Year Allocation Three [Member]
Multiemployer Plans [Line Items]
Cash payment			$ 2,245