Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Cash	$ 46,445	$ 59,455
Cash equivalents	34,622	44,751
Restricted cash - letters of credit	9,671	9,769
Total cash and cash equivalents	$ 90,738	$ 113,975	$ 117,474	$ 156,374