Quarterly report pursuant to Section 13 or 15(d)

Assets Held for Sale - Significant Assets Included in Assets Held for Sale (Details)

v3.10.0.1
Assets Held for Sale - Significant Assets Included in Assets Held for Sale (Details) - Disposal Group, Held-for-sale, Not Discontinued Operations
$ in Thousands
Jun. 30, 2018
USD ($)
Long Lived Assets Held-for-sale [Line Items]  
Less: accumulated depreciation $ (44,085)
Total assets held for sale 43,797
Texas North Yard  
Long Lived Assets Held-for-sale [Line Items]  
Less: accumulated depreciation (43,787)
Total assets held for sale 41,908
Shipyard Division Assets  
Long Lived Assets Held-for-sale [Line Items]  
Less: accumulated depreciation (298)
Total assets held for sale 1,889
Land  
Long Lived Assets Held-for-sale [Line Items]  
Total assets held for sale, gross 2,157
Land | Texas North Yard  
Long Lived Assets Held-for-sale [Line Items]  
Total assets held for sale, gross 2,157
Land | Shipyard Division Assets  
Long Lived Assets Held-for-sale [Line Items]  
Total assets held for sale, gross 0
Buildings and improvements  
Long Lived Assets Held-for-sale [Line Items]  
Total assets held for sale, gross 28,368
Buildings and improvements | Texas North Yard  
Long Lived Assets Held-for-sale [Line Items]  
Total assets held for sale, gross 28,368
Buildings and improvements | Shipyard Division Assets  
Long Lived Assets Held-for-sale [Line Items]  
Total assets held for sale, gross 0
Machinery and equipment  
Long Lived Assets Held-for-sale [Line Items]  
Total assets held for sale, gross 57,357
Machinery and equipment | Texas North Yard  
Long Lived Assets Held-for-sale [Line Items]  
Total assets held for sale, gross 55,170
Machinery and equipment | Shipyard Division Assets  
Long Lived Assets Held-for-sale [Line Items]  
Total assets held for sale, gross $ 2,187