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Interest rate swaps - Interest rate derivatives (Details) - USD ($) $ in Millions | Jun. 30, 2022 | Dec. 31, 2021
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Interest Rate Swap Matured On 11/21/2027 |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Notional amount | $ 50.0 |
Fixed interest rate | 2.75% |
Asset (liability) | $ (0.1) | $ 0.0
Interest Rate Swap Matured On 11/21/2029 |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Notional amount | $ 50.0 |
Fixed interest rate | 2.78% |
Asset (liability) | $ (0.1) | 0.0
Interest Rate Swap Matured On 09/01/2035 |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Notional amount | 24.0 |
Asset (liability) | $ (0.6) | (5.3)
Interest Rate Swap Matured On 09/01/2035 | Minimum |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Fixed interest rate | 4.88% |
Interest Rate Swap Matured On 09/01/2035 | Maximum |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Fixed interest rate | 5.05% |
Interest Rate Swap Matured On 10/01/2031 |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Notional amount | $ 13.0 |
Fixed interest rate | 2.79% |
Asset (liability) | $ 1.0 | $ 0.3

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