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Derivative Instruments and Hedging Activities - Effect of Derivative on Income Statement (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |  |
Unrealized gain (loss) on derivative instruments | $ 44,432 | $ 16,926 | $ (38,950)
Gain (loss) in derivative instruments not designated as hedges | 44,432 | 16,926 | (38,950)
Derivatives Not Designated as Hedges |  |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |  |
Unrealized gain (loss) on derivative instruments | 86,063 | 8,870 | (37,268)
Gain (loss) on derivative instruments | Derivatives Not Designated as Hedges |  |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |  |
Realized gain (loss) on derivative instruments | $ (41,631) | $ 8,056 | $ (1,682)

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- Definition The realized gain (loss) on derivative instruments from the difference between the book value and the sale price of options, swaps, futures, forward contracts, and other derivative instruments. This element refers to the gain (loss) included in earnings. + References No definition available. + Details
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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. + Details
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- Definition Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4CC -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109998890-113959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959 + Details
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- Definition The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585 + Details
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