Share-Based Compensation - Stock option valuation assumptions (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-Based Compensation
Weighted average fair value of options granted (in dollars per share)		$ 111.23	$ 72.69
Options exercised	0	0	0
Total fair value of option vested during the period		$ 0.2	$ 0.1
Employee Stock Option [Member]
Share-Based Compensation
Dividend yield (as a percent)		0.00%	0.00%
Expected volatility (as a percent)		111.50%	102.50%
Expected term (in years)		4 years	4 years
Employee Stock Option [Member] | Weighted Average
Share-Based Compensation
Risk free interest rate (as a percent)		3.69%	0.72%