Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Cash	$ 57,008	$ 34,707
Cash equivalents	70,689	70,826
Restricted cash - letters of credit	6,927	7,170
Total cash and cash equivalents	$ 134,624	$ 112,703	$ 113,975	$ 156,374