Commitments and Contingencies - Schedule of Contributions made to Multiemployer Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Multiemployer Plans [Line Items]
Contributions	$ 12,442	$ 11,977	$ 11,992
Pension Plans [Member]
Multiemployer Plans [Line Items]
Contributions	3,035	3,155	3,077
Pension Plans [Member] | Multiemployer Plan, Individually Insignificant Multiemployer Plans [Member]
Multiemployer Plans [Line Items]
Contributions	900	800	700
Health Plans [Member]
Multiemployer Plans [Line Items]
Contributions	8,551	8,280	8,296
Health Plans [Member] | Multiemployer Plan, Individually Insignificant Multiemployer Plans [Member]
Multiemployer Plans [Line Items]
Contributions	1,600	1,600	1,400
Other [Member]
Multiemployer Plans [Line Items]
Contributions	856	542	619
Other [Member] | Multiemployer Plan, Individually Insignificant Multiemployer Plans [Member]
Multiemployer Plans [Line Items]
Contributions	$ 200	$ 200	$ 200