Share-Based Compensation - Restricted shares based on market conditions (Details) - Restricted shares based on market conditions - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-Based Compensation
Shares awarded during period	47,622	61,997	22,931
Vesting period	3 years	3 years	3 years
Aggregate fair value at grant date	$ 2.3	$ 2.2	$ 2.5
Assumptions used to value grant date fair value
Risk free interest rate (as a percent)	1.03%	0.18%	1.57%
Expected volatility (as a percent)	92.00%	108.00%	74.00%
Closing stock price at grant date (in dollars per share)	$ 81.09	$ 60.62	$ 148.00
Expected term (in years)	3 years	3 years	3 years
Restricted shares outstanding
Outstanding at the beginning of the period (in shares))	85,000
Granted (in shares)	47,622	61,997	22,931
Outstanding at the end of the period (in shares)	133,000	85,000
Weighted-Average Grant-Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 55.29
Granted (in dollars per share)	49
Outstanding at the end of the period (in dollars per share)	$ 53.03	$ 55.29
Total future compensation cost related to unvested awards	$ 2.3
Recognition period	1 year 8 months 4 days