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Derivative Instruments - Interest rate swap agreement (Details) $ in Millions | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | ---
Sep. 30, 2020 USD ($) agreement | Sep. 30, 2019 USD ($) | Sep. 30, 2020 USD ($) agreement | Sep. 30, 2019 USD ($) | Dec. 31, 2019 USD ($) agreement | Dec. 31, 2016 agreement
Interest rate contract |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Borrowings at variable interest rates | $ 524.4 |  | $ 524.4 |  | $ 404.3 |
Number of interest rate swap agreements | agreement | 2 |  | 2 |  | 1 | 1
Derivative, notional amount | $ 100.0 |  | $ 100.0 |  | $ 100.0 |
Net fair value of swap liability | 4.8 |  | 4.8 |  | $ 1.7 |
Interest expense for derivative instruments | $ 0.7 | $ (0.1) | $ 1.3 | $ (0.5) |  |
2016 swap agreement |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Remaining maturity term |  |  | 7 months |  |  |
2019 swap agreement |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Remaining maturity term |  |  | 45 months |  |  |

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- Definition Fair value, after offset of derivative asset, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be and before offset against a right to receive collateral under a master netting arrangement. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=109980867&loc=d3e41678-113959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226006-175313 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 + 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 Nominal or face amount used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959 + Details
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- Definition Period remaining until the derivative contract matures, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition The portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time. + References No definition available. + Details
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- Definition Represents the amount of benefit recorded to net finance costs related expired derivative contracts. + References No definition available. + Details
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