Fair value measurements - Summary of Fair Value of Financial Instruments (Details) - USD ($)	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Funding obligation	$ 291,034	$ 268,976
Operating lease liabilities	4,281,850	4,370,635
Long-term debt	3,227,362	3,228,449
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Funding obligation	167,589	170,338
Operating lease liabilities	5,733,407	6,149,369
Long-term debt	$ 2,094,902	$ 2,303,648

Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant