Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Cash	$ 36,065	$ 59,455
Cash equivalents	33,927	44,751
Restricted cash - letters of credit	9,675	9,769
Total cash and cash equivalents	$ 79,667	$ 113,975	$ 80,452	$ 156,374