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Derivative Instruments - Location and Amounts of Derivative Gains and Losses in Condensed Consolidated Statements of Income (Details) - Derivatives not designated as hedging instruments - Interest rate swaps - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Net unrealized (loss) gain on financial instruments |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Net unrealized (loss) gain on financial instruments | $ (27,569) | $ (35,363) | $ 3,772
Financing interest expense |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Net unrealized (loss) gain on financial instruments | $ 15,842 | $ (5,411) | $ (6,160)

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- Definition The aggregate net gain (loss) on price risk derivatives included in earnings in the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5618551-113959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624171-113959 + Details
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