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Employee Retirement Plans - Global Marine Systems (Guernsey) Pension Plan (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2016
USD ($)
contribution
Dec. 31, 2014
USD ($)
Dec. 31, 2015
USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Defined contribution section employees contribution (as a percent) 50.00%    
Market value of defined benefit plan assets $ 170,772 $ 181,877 $ 172,511
Global Marine Systems (Guernsey) Pension Plan      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Actuarial valuation assumption used, pre-retirement return on investment per year (as a percent) 5.30%    
Actuarial valuation assumption used, post-retirement return on investment per year (as a percent) 4.40%    
Inflation rate percentage 3.70%    
Expected rate of pensions increase per year (as a percent) 3.30%    
Market value of defined benefit plan assets   3,000  
Amount of past service shortfall   $ 200  
Percentage of funding ratio   93.00%  
Number of annual contributions | contribution 7    
Amount of annual contributions $ 100    
Global Marine Systems (Guernsey) Pension Plan | Minimum      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Defined benefit, minimum employees contributions percentage 5.00%    
Defined contribution section employees contribution (as a percent) 2.00%    
Global Marine Systems (Guernsey) Pension Plan | Maximum      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Defined benefit, minimum employees contributions percentage 8.00%    
Defined contribution section employees contribution (as a percent) 7.50%