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Commitments and contingencies Commitments and contingencies - Credit Losses (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | ---
Sep. 30, 2020 | Sep. 30, 2020 | Jun. 30, 2020 | Dec. 31, 2019
Commitments and Contingencies [Roll Forward] |  |  |  |
Balance at beginning of period | $ 113,129 | $ 31,139 |  |
Balance at end of period | 183,973 | 183,973 |  |
Unfunded Commitments |  |  |  |
Commitments and Contingencies [Roll Forward] |  |  |  |
Balance at beginning of period | 6,500 | 0 |  |
Initial recognition of allowance for credit losses |  |  | $ 0 | $ 2,947
Increase in allowance for credit losses from unfunded commitments acquired in business combination | 10,429 | 10,499 |  |
Provision for credit losses on unfunded commitments | (862) | 2,621 |  |
Balance at end of period | $ 16,067 | $ 16,067 |  |

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