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Derivatives - Foreign Currency Derivative Contracts (Details) - Not Designated as Hedging Instrument
$ in Thousands
Mar. 31, 2017
USD ($)
$ / £
$ / €
$ / NOK
$ / CAD
Dec. 31, 2016
USD ($)
$ / £
$ / €
$ / NOK
$ / CAD
Foreign currency contracts | Canadian dollar    
Derivative [Line Items]    
Notional Amount $ 5,785 $ 4,553
Contractual Exchange Rate | $ / CAD 1.3483 1.3179
Foreign currency contracts | Euro    
Derivative [Line Items]    
Notional Amount $ 5,657 $ 4,753
Contractual Exchange Rate | $ / € 1.0674 1.0563
Foreign currency contracts | Norwegian kroner    
Derivative [Line Items]    
Notional Amount $ 7,192 $ 3,643
Contractual Exchange Rate | $ / NOK 8.6204 8.5101
Foreign currency contracts | Pound sterling    
Derivative [Line Items]    
Notional Amount $ 5,958 $ 3,908
Contractual Exchange Rate | $ / £ 1.2160 1.2607
Foreign currency contracts, settlement date January 13, 2017 | Euro    
Derivative [Line Items]    
Notional Amount   $ 2,558
Contractual Exchange Rate | $ / €   1.0659