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Derivative Instruments - Interest rate swap agreement (Details) $ in Millions | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2020 USD ($) agreement | Dec. 31, 2019 USD ($) | Jan. 31, 2021 USD ($) agreement | Oct. 31, 2019 USD ($) | Dec. 31, 2016 USD ($)
Interest rate contracts |  |  |  |  |
Derivative instruments |  |  |  |  |
Borrowings at variable interest rates | $ 783.1 | $ 404.3 |  |  |
Number of interest rate swap agreements | agreement | 2 |  |  |  |
Notional amount outstanding |  |  |  | $ 100.0 | $ 100.0
Net fair value of swap liability | $ 4.0 | 1.7 |  |  |
Interest rate contracts | Subsequent Event |  |  |  |  |
Derivative instruments |  |  |  |  |
Number of interest rate swap agreements | agreement |  |  | 4 |  |
Notional amount outstanding |  |  | $ 100.0 |  |
Interest rate contracts | Level 2 | Fair Value, Recurring |  |  |  |  |
Derivative instruments |  |  |  |  |
Loss recorded to net finance costs | $ 2.0 | $ (0.7) |  |  |
2016 Swap Agreement |  |  |  |  |
Derivative instruments |  |  |  |  |
Remaining maturity term | 4 months |  |  |  |
2019 Swap Agreement |  |  |  |  |
Derivative instruments |  |  |  |  |
Remaining maturity term | 42 months |  |  |  |
Swap agreement maturing January 2024 | Subsequent Event |  |  |  |  |
Derivative instruments |  |  |  |  |
Number of interest rate swap agreements | agreement |  |  | 2 |  |
Swap agreement maturing January 2026 | Subsequent Event |  |  |  |  |
Derivative instruments |  |  |  |  |
Number of interest rate swap agreements | agreement |  |  | 2 |  |

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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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