Summary of significant accounting policies - Additional Information (Details)
|
9 Months Ended |
12 Months Ended |
|
|
Sep. 30, 2021
USD ($)
segment
|
Dec. 31, 2020
USD ($)
segment
reporting_unit
|
Dec. 31, 2019
USD ($)
|
Jan. 01, 2019
USD ($)
|
| Accounting Policies [Abstract] |
|
|
|
|
| Number of reporting segments | segment |
2
|
1
|
|
|
| Other than temporary impairment losses |
|
$ 0
|
$ 0
|
|
| Property, Plant and Equipment [Line Items] |
|
|
|
|
| Number of reporting units | reporting_unit |
|
1
|
|
|
| Impairment of goodwill |
|
$ 0
|
0
|
|
| Allowances for uncollectible reinsurance recoverable |
|
0
|
0
|
|
| HIF paid |
|
8,022,000
|
0
|
|
| New Accounting Pronouncements or Change in Accounting Principle [Line Items] |
|
|
|
|
| Operating lease ROU assets |
$ 5,828,000
|
7,882,000
|
$ 11,097,000
|
|
| Operating lease liabilities |
$ 8,547,000
|
$ 11,144,000
|
|
|
| Minimum |
|
|
|
|
| Property, Plant and Equipment [Line Items] |
|
|
|
|
| Useful lives of property and equipment, net |
|
3 years
|
|
|
| Maximum |
|
|
|
|
| Property, Plant and Equipment [Line Items] |
|
|
|
|
| Useful lives of property and equipment, net |
|
7 years
|
|
|
| Cumulative Effect, Period of Adoption, Adjustment |
|
|
|
|
| New Accounting Pronouncements or Change in Accounting Principle [Line Items] |
|
|
|
|
| Operating lease ROU assets |
|
|
|
$ 14,300,000
|
| Operating lease liabilities |
|
|
|
$ 17,400,000
|