Stock-based compensation - Weighted average fair value of options at the date of grant and the intrinsic value of options exercised (Details) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Stock-based compensation
Total intrinsic value of options exercised	$ 2,482	$ 104,559	$ 17,158
Below Market Price
Stock-based compensation
Options granted with an weighted average exercise price	$ 2.58	$ 12.21	$ 5.58
Below Market Price | Employees | Preferred stock
Stock-based compensation
Options granted with an weighted average exercise price	2.58	12.21	5.58
At Market Price
Stock-based compensation
Options granted with an weighted average exercise price	8.5	8.29	4.32
At Market Price | Management employees
Stock-based compensation
Options granted with an weighted average exercise price	0	0	0
At Market Price | Employees | Common stock
Stock-based compensation
Options granted with an weighted average exercise price	8.5	8.29	4.32
Above Market Price
Stock-based compensation
Options granted with an weighted average exercise price	0	0	0
Above Market Price | Management employees
Stock-based compensation
Options granted with an weighted average exercise price	0	0	0
Above Market Price | Employees | Preferred stock
Stock-based compensation
Options granted with an weighted average exercise price	$ 0	$ 0	$ 0