Summary of Significant Accounting Policies - Reconciliation of shares used to determine net income per share (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Summary of Significant Accounting Policies
Net income	$ 13,582	$ 29,356	$ 48,302	$ 98,721
Weighted average number of shares - basic	45,404,963	45,063,810	45,348,072	44,935,739
Shares underlying options	1,940,417	2,117,614	1,971,392	2,117,271
Weighted average number of shares outstanding - diluted	47,345,380	47,181,424	47,319,464	47,053,010