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Financial Instruments - Summary of Outstanding Interest Rate Swap Agreement (Details) - Interest rate swap - Cash Flow Hedging
$ in Millions
12 Months Ended
Dec. 31, 2017
USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]  
Derivative contract term (years) 3 years
Aggregate Notional Amount $ 350.0
LIBOR  
Derivative Instruments and Hedging Activities Disclosures [Line Items]  
Spread on receive rate 1.75%
Receive Rate as of December 31, 2017 3.30%
Pay Rate 3.50%