Derivative Instruments and Hedging Activities - Summary of Cross Currency Swaps (Details) - Cross currency swaps - NIBOR kr in Thousands, $ in Thousands	6 Months Ended
Jun. 30, 2018 USD ($)	Jun. 30, 2018 NOK (kr)
Derivative [Line Items]
Notional Amount	$ 162,200	kr 1,000,000
Floating Rate Receivable Reference Margin	4.25%	4.25%
Fixed Rate Payable	7.45%	7.45%
Fair Value / Asset (Liability)	$ (42,118)
Remaining Term (years)	7 months 6 days

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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- Definition

Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Variable interest rate in effect as of the balance sheet date related to the interest rate derivative.

+ References

No definition available.

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- Definition

Fair value as of the balance sheet date of all foreign currency derivatives not designated as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

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